// Copyright 2012 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

/** \mainpage V8 API Reference Guide
 *
 * V8 is Google's open source JavaScript engine.
 *
 * This set of documents provides reference material generated from the
 * V8 header file, include/v8.h.
 *
 * For other documentation see http://code.google.com/apis/v8/
 */

#ifndef INCLUDE_V8_H_
#define INCLUDE_V8_H_

#include <stddef.h>
#include <stdint.h>
#include <stdio.h>
#include <memory>
#include <utility>
#include <vector>

#include "v8-version.h"  // NOLINT(build/include)
#include "v8config.h"    // NOLINT(build/include)

// We reserve the V8_* prefix for macros defined in V8 public API and
// assume there are no name conflicts with the embedder's code.

#ifdef V8_OS_WIN

// Setup for Windows DLL export/import. When building the V8 DLL the
// BUILDING_V8_SHARED needs to be defined. When building a program which uses
// the V8 DLL USING_V8_SHARED needs to be defined. When either building the V8
// static library or building a program which uses the V8 static library neither
// BUILDING_V8_SHARED nor USING_V8_SHARED should be defined.
#if defined(BUILDING_V8_SHARED) && defined(USING_V8_SHARED)
#error both BUILDING_V8_SHARED and USING_V8_SHARED are set - please check the\
build configuration to ensure that at most one of these is set
#endif

#ifdef BUILDING_V8_SHARED
# define V8_EXPORT __declspec(dllexport)
#elif USING_V8_SHARED
# define V8_EXPORT __declspec(dllimport)
#else
# define V8_EXPORT
#endif  // BUILDING_V8_SHARED

#else  // V8_OS_WIN

// Setup for Linux shared library export.
#if V8_HAS_ATTRIBUTE_VISIBILITY
# ifdef BUILDING_V8_SHARED
#  define V8_EXPORT __attribute__ ((visibility("default")))
# else
#  define V8_EXPORT
# endif
#else
# define V8_EXPORT
#endif

#endif  // V8_OS_WIN

/**
 * The v8 JavaScript engine.
 */
namespace v8 {

class AccessorSignature;
class Array;
class ArrayBuffer;
class Boolean;
class BooleanObject;
class Context;
class CpuProfiler;
class Data;
class Date;
class External;
class Function;
class FunctionTemplate;
class HeapProfiler;
class ImplementationUtilities;
class Int32;
class Integer;
class Isolate;
template <class T>
class Maybe;
class Name;
class Number;
class NumberObject;
class Object;
class ObjectOperationDescriptor;
class ObjectTemplate;
class Platform;
class Primitive;
class Promise;
class PropertyDescriptor;
class Proxy;
class RawOperationDescriptor;
class Script;
class SharedArrayBuffer;
class Signature;
class StartupData;
class StackFrame;
class StackTrace;
class String;
class StringObject;
class Symbol;
class SymbolObject;
class Private;
class Uint32;
class Utils;
class Value;
template <class T> class Local;
template <class T>
class MaybeLocal;
template <class T> class Eternal;
template<class T> class NonCopyablePersistentTraits;
template<class T> class PersistentBase;
template <class T, class M = NonCopyablePersistentTraits<T> >
class Persistent;
template <class T>
class Global;
template<class K, class V, class T> class PersistentValueMap;
template <class K, class V, class T>
class PersistentValueMapBase;
template <class K, class V, class T>
class GlobalValueMap;
template<class V, class T> class PersistentValueVector;
template<class T, class P> class WeakCallbackObject;
class FunctionTemplate;
class ObjectTemplate;
class Data;
template<typename T> class FunctionCallbackInfo;
template<typename T> class PropertyCallbackInfo;
class StackTrace;
class StackFrame;
class Isolate;
class CallHandlerHelper;
class EscapableHandleScope;
template<typename T> class ReturnValue;

namespace experimental {
class FastAccessorBuilder;
}  // namespace experimental

namespace internal {
class Arguments;
class Heap;
class HeapObject;
class Isolate;
class Object;
struct StreamedSource;
template<typename T> class CustomArguments;
class PropertyCallbackArguments;
class FunctionCallbackArguments;
class GlobalHandles;
}  // namespace internal


/**
 * General purpose unique identifier.
 */
class UniqueId {
    public:
        explicit UniqueId(intptr_t data)
            : data_(data) {}

        bool operator==(const UniqueId& other) const {
            return data_ == other.data_;
        }

        bool operator!=(const UniqueId& other) const {
            return data_ != other.data_;
        }

        bool operator<(const UniqueId& other) const {
            return data_ < other.data_;
        }

    private:
        intptr_t data_;
};

// --- Handles ---

#define TYPE_CHECK(T, S)                                       \
  while (false) {                                              \
    *(static_cast<T* volatile*>(0)) = static_cast<S*>(0);      \
  }


/**
 * An object reference managed by the v8 garbage collector.
 *
 * All objects returned from v8 have to be tracked by the garbage
 * collector so that it knows that the objects are still alive.  Also,
 * because the garbage collector may move objects, it is unsafe to
 * point directly to an object.  Instead, all objects are stored in
 * handles which are known by the garbage collector and updated
 * whenever an object moves.  Handles should always be passed by value
 * (except in cases like out-parameters) and they should never be
 * allocated on the heap.
 *
 * There are two types of handles: local and persistent handles.
 * Local handles are light-weight and transient and typically used in
 * local operations.  They are managed by HandleScopes.  Persistent
 * handles can be used when storing objects across several independent
 * operations and have to be explicitly deallocated when they're no
 * longer used.
 *
 * It is safe to extract the object stored in the handle by
 * dereferencing the handle (for instance, to extract the Object* from
 * a Local<Object>); the value will still be governed by a handle
 * behind the scenes and the same rules apply to these values as to
 * their handles.
 */
template <class T>
class Local {
    public:
        V8_INLINE Local() : val_(0) {}
        template <class S>
        V8_INLINE Local(Local<S> that)
            : val_(reinterpret_cast<T*>(*that)) {
            /**
             * This check fails when trying to convert between incompatible
             * handles. For example, converting from a Local<String> to a
             * Local<Number>.
             */
            TYPE_CHECK(T, S);
        }

        /**
         * Returns true if the handle is empty.
         */
        V8_INLINE bool IsEmpty() const {
            return val_ == 0;
        }

        /**
         * Sets the handle to be empty. IsEmpty() will then return true.
         */
        V8_INLINE void Clear() {
            val_ = 0;
        }

        V8_INLINE T* operator->() const {
            return val_;
        }

        V8_INLINE T* operator*() const {
            return val_;
        }

        /**
         * Checks whether two handles are the same.
         * Returns true if both are empty, or if the objects
         * to which they refer are identical.
         * The handles' references are not checked.
         */
        template <class S>
        V8_INLINE bool operator==(const Local<S>& that) const {
            internal::Object** a = reinterpret_cast<internal::Object**>(this->val_);
            internal::Object** b = reinterpret_cast<internal::Object**>(that.val_);
            if (a == 0) {
                return b == 0;
            }
            if (b == 0) {
                return false;
            }
            return *a == *b;
        }

        template <class S> V8_INLINE bool operator==(
            const PersistentBase<S>& that) const {
            internal::Object** a = reinterpret_cast<internal::Object**>(this->val_);
            internal::Object** b = reinterpret_cast<internal::Object**>(that.val_);
            if (a == 0) {
                return b == 0;
            }
            if (b == 0) {
                return false;
            }
            return *a == *b;
        }

        /**
         * Checks whether two handles are different.
         * Returns true if only one of the handles is empty, or if
         * the objects to which they refer are different.
         * The handles' references are not checked.
         */
        template <class S>
        V8_INLINE bool operator!=(const Local<S>& that) const {
            return !operator==(that);
        }

        template <class S> V8_INLINE bool operator!=(
            const Persistent<S>& that) const {
            return !operator==(that);
        }

        template <class S> V8_INLINE static Local<T> Cast(Local<S> that) {
#ifdef V8_ENABLE_CHECKS
            // If we're going to perform the type check then we have to check
            // that the handle isn't empty before doing the checked cast.
            if (that.IsEmpty()) {
                return Local<T>();
            }
#endif
            return Local<T>(T::Cast(*that));
        }

        template <class S>
        V8_INLINE Local<S> As() const {
            return Local<S>::Cast(*this);
        }

        /**
         * Create a local handle for the content of another handle.
         * The referee is kept alive by the local handle even when
         * the original handle is destroyed/disposed.
         */
        V8_INLINE static Local<T> New(Isolate* isolate, Local<T> that);
        V8_INLINE static Local<T> New(Isolate* isolate,
                                      const PersistentBase<T>& that);

    private:
        friend class Utils;
        template<class F> friend class Eternal;
        template<class F> friend class PersistentBase;
        template<class F, class M> friend class Persistent;
        template<class F> friend class Local;
        template <class F>
        friend class MaybeLocal;
        template<class F> friend class FunctionCallbackInfo;
        template<class F> friend class PropertyCallbackInfo;
        friend class String;
        friend class Object;
        friend class Context;
        friend class Private;
        template<class F> friend class internal::CustomArguments;
        friend Local<Primitive> Undefined(Isolate* isolate);
        friend Local<Primitive> Null(Isolate* isolate);
        friend Local<Boolean> True(Isolate* isolate);
        friend Local<Boolean> False(Isolate* isolate);
        friend class HandleScope;
        friend class EscapableHandleScope;
        template <class F1, class F2, class F3>
        friend class PersistentValueMapBase;
        template<class F1, class F2> friend class PersistentValueVector;
        template <class F>
        friend class ReturnValue;

        explicit V8_INLINE Local(T* that) : val_(that) {}
        V8_INLINE static Local<T> New(Isolate* isolate, T* that);
        T* val_;
};


#if !defined(V8_IMMINENT_DEPRECATION_WARNINGS)
// Handle is an alias for Local for historical reasons.
template <class T>
using Handle = Local<T>;
#endif


/**
 * A MaybeLocal<> is a wrapper around Local<> that enforces a check whether
 * the Local<> is empty before it can be used.
 *
 * If an API method returns a MaybeLocal<>, the API method can potentially fail
 * either because an exception is thrown, or because an exception is pending,
 * e.g. because a previous API call threw an exception that hasn't been caught
 * yet, or because a TerminateExecution exception was thrown. In that case, an
 * empty MaybeLocal is returned.
 */
template <class T>
class MaybeLocal {
    public:
        V8_INLINE MaybeLocal() : val_(nullptr) {}
        template <class S>
        V8_INLINE MaybeLocal(Local<S> that)
            : val_(reinterpret_cast<T*>(*that)) {
            TYPE_CHECK(T, S);
        }

        V8_INLINE bool IsEmpty() const {
            return val_ == nullptr;
        }

        template <class S>
        V8_WARN_UNUSED_RESULT V8_INLINE bool ToLocal(Local<S>* out) const {
            out->val_ = IsEmpty() ? nullptr : this->val_;
            return !IsEmpty();
        }

        // Will crash if the MaybeLocal<> is empty.
        V8_INLINE Local<T> ToLocalChecked();

        template <class S>
        V8_INLINE Local<S> FromMaybe(Local<S> default_value) const {
            return IsEmpty() ? default_value : Local<S>(val_);
        }

    private:
        T* val_;
};


// Eternal handles are set-once handles that live for the life of the isolate.
template <class T> class Eternal {
    public:
        V8_INLINE Eternal() : index_(kInitialValue) { }
        template<class S>
        V8_INLINE Eternal(Isolate* isolate, Local<S> handle) : index_(kInitialValue) {
            Set(isolate, handle);
        }
        // Can only be safely called if already set.
        V8_INLINE Local<T> Get(Isolate* isolate);
        V8_INLINE bool IsEmpty() {
            return index_ == kInitialValue;
        }
        template<class S> V8_INLINE void Set(Isolate* isolate, Local<S> handle);

    private:
        static const int kInitialValue = -1;
        int index_;
};


static const int kInternalFieldsInWeakCallback = 2;


template <typename T>
class WeakCallbackInfo {
    public:
        typedef void (*Callback)(const WeakCallbackInfo<T>& data);

        WeakCallbackInfo(Isolate* isolate, T* parameter,
                         void* internal_fields[kInternalFieldsInWeakCallback],
                         Callback* callback)
            : isolate_(isolate), parameter_(parameter), callback_(callback) {
            for (int i = 0; i < kInternalFieldsInWeakCallback; ++i) {
                internal_fields_[i] = internal_fields[i];
            }
        }

        V8_INLINE Isolate* GetIsolate() const {
            return isolate_;
        }
        V8_INLINE T* GetParameter() const {
            return parameter_;
        }
        V8_INLINE void* GetInternalField(int index) const;

        V8_INLINE V8_DEPRECATED("use indexed version",
                                void* GetInternalField1() const) {
            return internal_fields_[0];
        }
        V8_INLINE V8_DEPRECATED("use indexed version",
                                void* GetInternalField2() const) {
            return internal_fields_[1];
        }

        V8_DEPRECATED("Not realiable once SetSecondPassCallback() was used.",
                      bool IsFirstPass() const) {
            return callback_ != nullptr;
        }

        // When first called, the embedder MUST Reset() the Global which triggered the
        // callback. The Global itself is unusable for anything else. No v8 other api
        // calls may be called in the first callback. Should additional work be
        // required, the embedder must set a second pass callback, which will be
        // called after all the initial callbacks are processed.
        // Calling SetSecondPassCallback on the second pass will immediately crash.
        void SetSecondPassCallback(Callback callback) const {
            *callback_ = callback;
        }

    private:
        Isolate* isolate_;
        T* parameter_;
        Callback* callback_;
        void* internal_fields_[kInternalFieldsInWeakCallback];
};


// kParameter will pass a void* parameter back to the callback, kInternalFields
// will pass the first two internal fields back to the callback, kFinalizer
// will pass a void* parameter back, but is invoked before the object is
// actually collected, so it can be resurrected. In the last case, it is not
// possible to request a second pass callback.
enum class WeakCallbackType { kParameter, kInternalFields, kFinalizer };

/**
 * A reporter class that embedder will use to report reachable references found
 * by EmbedderHeapTracer.
 */
class V8_EXPORT EmbedderReachableReferenceReporter {
    public:
        virtual void ReportExternalReference(Value* object) = 0;
        virtual ~EmbedderReachableReferenceReporter() = default;
};

/**
 * An object reference that is independent of any handle scope.  Where
 * a Local handle only lives as long as the HandleScope in which it was
 * allocated, a PersistentBase handle remains valid until it is explicitly
 * disposed.
 *
 * A persistent handle contains a reference to a storage cell within
 * the v8 engine which holds an object value and which is updated by
 * the garbage collector whenever the object is moved.  A new storage
 * cell can be created using the constructor or PersistentBase::Reset and
 * existing handles can be disposed using PersistentBase::Reset.
 *
 */
template <class T> class PersistentBase {
    public:
        /**
         * If non-empty, destroy the underlying storage cell
         * IsEmpty() will return true after this call.
         */
        V8_INLINE void Reset();
        /**
         * If non-empty, destroy the underlying storage cell
         * and create a new one with the contents of other if other is non empty
         */
        template <class S>
        V8_INLINE void Reset(Isolate* isolate, const Local<S>& other);

        /**
         * If non-empty, destroy the underlying storage cell
         * and create a new one with the contents of other if other is non empty
         */
        template <class S>
        V8_INLINE void Reset(Isolate* isolate, const PersistentBase<S>& other);

        V8_INLINE bool IsEmpty() const {
            return val_ == NULL;
        }
        V8_INLINE void Empty() {
            val_ = 0;
        }

        V8_INLINE Local<T> Get(Isolate* isolate) const {
            return Local<T>::New(isolate, *this);
        }

        template <class S>
        V8_INLINE bool operator==(const PersistentBase<S>& that) const {
            internal::Object** a = reinterpret_cast<internal::Object**>(this->val_);
            internal::Object** b = reinterpret_cast<internal::Object**>(that.val_);
            if (a == NULL) {
                return b == NULL;
            }
            if (b == NULL) {
                return false;
            }
            return *a == *b;
        }

        template <class S>
        V8_INLINE bool operator==(const Local<S>& that) const {
            internal::Object** a = reinterpret_cast<internal::Object**>(this->val_);
            internal::Object** b = reinterpret_cast<internal::Object**>(that.val_);
            if (a == NULL) {
                return b == NULL;
            }
            if (b == NULL) {
                return false;
            }
            return *a == *b;
        }

        template <class S>
        V8_INLINE bool operator!=(const PersistentBase<S>& that) const {
            return !operator==(that);
        }

        template <class S>
        V8_INLINE bool operator!=(const Local<S>& that) const {
            return !operator==(that);
        }

        /**
         *  Install a finalization callback on this object.
         *  NOTE: There is no guarantee as to *when* or even *if* the callback is
         *  invoked. The invocation is performed solely on a best effort basis.
         *  As always, GC-based finalization should *not* be relied upon for any
         *  critical form of resource management!
         */
        template <typename P>
        V8_INLINE void SetWeak(P* parameter,
                               typename WeakCallbackInfo<P>::Callback callback,
                               WeakCallbackType type);

        /**
         * Turns this handle into a weak phantom handle without finalization callback.
         * The handle will be reset automatically when the garbage collector detects
         * that the object is no longer reachable.
         * A related function Isolate::NumberOfPhantomHandleResetsSinceLastCall
         * returns how many phantom handles were reset by the garbage collector.
         */
        V8_INLINE void SetWeak();

        template<typename P>
        V8_INLINE P* ClearWeak();

        // TODO(dcarney): remove this.
        V8_INLINE void ClearWeak() {
            ClearWeak<void>();
        }

        /**
         * Deprecated.
         * TODO(hlopko): remove once migration to reporter is finished.
         */
        V8_INLINE void RegisterExternalReference(Isolate* isolate) const {}

        /**
         * Allows the embedder to tell the v8 garbage collector that a certain object
         * is alive. Only allowed when the embedder is asked to trace its heap by
         * EmbedderHeapTracer.
         */
        V8_INLINE void RegisterExternalReference(
            EmbedderReachableReferenceReporter* reporter) const;

        /**
         * Marks the reference to this object independent. Garbage collector is free
         * to ignore any object groups containing this object. Weak callback for an
         * independent handle should not assume that it will be preceded by a global
         * GC prologue callback or followed by a global GC epilogue callback.
         */
        V8_INLINE void MarkIndependent();

        /**
         * Marks the reference to this object partially dependent. Partially dependent
         * handles only depend on other partially dependent handles and these
         * dependencies are provided through object groups. It provides a way to build
         * smaller object groups for young objects that represent only a subset of all
         * external dependencies. This mark is automatically cleared after each
         * garbage collection.
         */
        V8_INLINE V8_DEPRECATED(
            "deprecated optimization, do not use partially dependent groups",
            void MarkPartiallyDependent());

        /**
         * Marks the reference to this object as active. The scavenge garbage
         * collection should not reclaim the objects marked as active.
         * This bit is cleared after the each garbage collection pass.
         */
        V8_INLINE void MarkActive();

        V8_INLINE bool IsIndependent() const;

        /** Checks if the handle holds the only reference to an object. */
        V8_INLINE bool IsNearDeath() const;

        /** Returns true if the handle's reference is weak.  */
        V8_INLINE bool IsWeak() const;

        /**
         * Assigns a wrapper class ID to the handle. See RetainedObjectInfo interface
         * description in v8-profiler.h for details.
         */
        V8_INLINE void SetWrapperClassId(uint16_t class_id);

        /**
         * Returns the class ID previously assigned to this handle or 0 if no class ID
         * was previously assigned.
         */
        V8_INLINE uint16_t WrapperClassId() const;

        PersistentBase(const PersistentBase& other) = delete;  // NOLINT
        void operator=(const PersistentBase&) = delete;

    private:
        friend class Isolate;
        friend class Utils;
        template<class F> friend class Local;
        template<class F1, class F2> friend class Persistent;
        template <class F>
        friend class Global;
        template<class F> friend class PersistentBase;
        template<class F> friend class ReturnValue;
        template <class F1, class F2, class F3>
        friend class PersistentValueMapBase;
        template<class F1, class F2> friend class PersistentValueVector;
        friend class Object;

        explicit V8_INLINE PersistentBase(T* val) : val_(val) {}
        V8_INLINE static T* New(Isolate* isolate, T* that);

        T* val_;
};


/**
 * Default traits for Persistent. This class does not allow
 * use of the copy constructor or assignment operator.
 * At present kResetInDestructor is not set, but that will change in a future
 * version.
 */
template<class T>
class NonCopyablePersistentTraits {
    public:
        typedef Persistent<T, NonCopyablePersistentTraits<T> > NonCopyablePersistent;
        static const bool kResetInDestructor = false;
        template<class S, class M>
        V8_INLINE static void Copy(const Persistent<S, M>& source,
                                   NonCopyablePersistent* dest) {
            Uncompilable<Object>();
        }
        // TODO(dcarney): come up with a good compile error here.
        template<class O> V8_INLINE static void Uncompilable() {
            TYPE_CHECK(O, Primitive);
        }
};


/**
 * Helper class traits to allow copying and assignment of Persistent.
 * This will clone the contents of storage cell, but not any of the flags, etc.
 */
template<class T>
struct CopyablePersistentTraits {
    typedef Persistent<T, CopyablePersistentTraits<T> > CopyablePersistent;
    static const bool kResetInDestructor = true;
    template<class S, class M>
    static V8_INLINE void Copy(const Persistent<S, M>& source,
                               CopyablePersistent* dest) {
        // do nothing, just allow copy
    }
};


/**
 * A PersistentBase which allows copy and assignment.
 *
 * Copy, assignment and destructor bevavior is controlled by the traits
 * class M.
 *
 * Note: Persistent class hierarchy is subject to future changes.
 */
template <class T, class M> class Persistent : public PersistentBase<T> {
    public:
        /**
         * A Persistent with no storage cell.
         */
        V8_INLINE Persistent() : PersistentBase<T>(0) { }
        /**
         * Construct a Persistent from a Local.
         * When the Local is non-empty, a new storage cell is created
         * pointing to the same object, and no flags are set.
         */
        template <class S>
        V8_INLINE Persistent(Isolate* isolate, Local<S> that)
            : PersistentBase<T>(PersistentBase<T>::New(isolate, *that)) {
            TYPE_CHECK(T, S);
        }
        /**
         * Construct a Persistent from a Persistent.
         * When the Persistent is non-empty, a new storage cell is created
         * pointing to the same object, and no flags are set.
         */
        template <class S, class M2>
        V8_INLINE Persistent(Isolate* isolate, const Persistent<S, M2>& that)
            : PersistentBase<T>(PersistentBase<T>::New(isolate, *that)) {
            TYPE_CHECK(T, S);
        }
        /**
         * The copy constructors and assignment operator create a Persistent
         * exactly as the Persistent constructor, but the Copy function from the
         * traits class is called, allowing the setting of flags based on the
         * copied Persistent.
         */
        V8_INLINE Persistent(const Persistent& that) : PersistentBase<T>(0) {
            Copy(that);
        }
        template <class S, class M2>
        V8_INLINE Persistent(const Persistent<S, M2>& that) : PersistentBase<T>(0) {
            Copy(that);
        }
        V8_INLINE Persistent& operator=(const Persistent& that) { // NOLINT
            Copy(that);
            return *this;
        }
        template <class S, class M2>
        V8_INLINE Persistent& operator=(const Persistent<S, M2>& that) { // NOLINT
            Copy(that);
            return *this;
        }
        /**
         * The destructor will dispose the Persistent based on the
         * kResetInDestructor flags in the traits class.  Since not calling dispose
         * can result in a memory leak, it is recommended to always set this flag.
         */
        V8_INLINE ~Persistent() {
            if (M::kResetInDestructor) {
                this->Reset();
            }
        }

        // TODO(dcarney): this is pretty useless, fix or remove
        template <class S>
        V8_INLINE static Persistent<T>& Cast(const Persistent<S>& that) {  // NOLINT
#ifdef V8_ENABLE_CHECKS
            // If we're going to perform the type check then we have to check
            // that the handle isn't empty before doing the checked cast.
            if (!that.IsEmpty()) {
                T::Cast(*that);
            }
#endif
            return reinterpret_cast<Persistent<T>&>(const_cast<Persistent<S>&>(that));
        }

        // TODO(dcarney): this is pretty useless, fix or remove
        template <class S>
        V8_INLINE Persistent<S>& As() const {  // NOLINT
            return Persistent<S>::Cast(*this);
        }

    private:
        friend class Isolate;
        friend class Utils;
        template<class F> friend class Local;
        template<class F1, class F2> friend class Persistent;
        template<class F> friend class ReturnValue;

        explicit V8_INLINE Persistent(T* that) : PersistentBase<T>(that) {}
        V8_INLINE T* operator*() const {
            return this->val_;
        }
        template<class S, class M2>
        V8_INLINE void Copy(const Persistent<S, M2>& that);
};


/**
 * A PersistentBase which has move semantics.
 *
 * Note: Persistent class hierarchy is subject to future changes.
 */
template <class T>
class Global : public PersistentBase<T> {
    public:
        /**
         * A Global with no storage cell.
         */
        V8_INLINE Global() : PersistentBase<T>(nullptr) {}
        /**
         * Construct a Global from a Local.
         * When the Local is non-empty, a new storage cell is created
         * pointing to the same object, and no flags are set.
         */
        template <class S>
        V8_INLINE Global(Isolate* isolate, Local<S> that)
            : PersistentBase<T>(PersistentBase<T>::New(isolate, *that)) {
            TYPE_CHECK(T, S);
        }
        /**
         * Construct a Global from a PersistentBase.
         * When the Persistent is non-empty, a new storage cell is created
         * pointing to the same object, and no flags are set.
         */
        template <class S>
        V8_INLINE Global(Isolate* isolate, const PersistentBase<S>& that)
            : PersistentBase<T>(PersistentBase<T>::New(isolate, that.val_)) {
            TYPE_CHECK(T, S);
        }
        /**
         * Move constructor.
         */
        V8_INLINE Global(Global&& other) : PersistentBase<T>(other.val_) {  // NOLINT
            other.val_ = nullptr;
        }
        V8_INLINE ~Global() {
            this->Reset();
        }
        /**
         * Move via assignment.
         */
        template <class S>
        V8_INLINE Global& operator=(Global<S>&& rhs) {  // NOLINT
            TYPE_CHECK(T, S);
            if (this != &rhs) {
                this->Reset();
                this->val_ = rhs.val_;
                rhs.val_ = nullptr;
            }
            return *this;
        }
        /**
         * Pass allows returning uniques from functions, etc.
         */
        Global Pass() {
            return static_cast<Global&&>(*this);    // NOLINT
        }

        /*
         * For compatibility with Chromium's base::Bind (base::Passed).
         */
        typedef void MoveOnlyTypeForCPP03;

        Global(const Global&) = delete;
        void operator=(const Global&) = delete;

    private:
        template <class F>
        friend class ReturnValue;
        V8_INLINE T* operator*() const {
            return this->val_;
        }
};


// UniquePersistent is an alias for Global for historical reason.
template <class T>
using UniquePersistent = Global<T>;


/**
* A stack-allocated class that governs a number of local handles.
* After a handle scope has been created, all local handles will be
* allocated within that handle scope until either the handle scope is
* deleted or another handle scope is created.  If there is already a
* handle scope and a new one is created, all allocations will take
* place in the new handle scope until it is deleted.  After that,
* new handles will again be allocated in the original handle scope.
*
* After the handle scope of a local handle has been deleted the
* garbage collector will no longer track the object stored in the
* handle and may deallocate it.  The behavior of accessing a handle
* for which the handle scope has been deleted is undefined.
*/
class V8_EXPORT HandleScope {
    public:
        explicit HandleScope(Isolate* isolate);

        ~HandleScope();

        /**
         * Counts the number of allocated handles.
         */
        static int NumberOfHandles(Isolate* isolate);

        V8_INLINE Isolate* GetIsolate() const {
            return reinterpret_cast<Isolate*>(isolate_);
        }

        HandleScope(const HandleScope&) = delete;
        void operator=(const HandleScope&) = delete;
        void* operator new(size_t size) = delete;
        void operator delete(void*, size_t) = delete;

    protected:
        V8_INLINE HandleScope() {}

        void Initialize(Isolate* isolate);

        static internal::Object** CreateHandle(internal::Isolate* isolate,
                                               internal::Object* value);

    private:
        // Uses heap_object to obtain the current Isolate.
        static internal::Object** CreateHandle(internal::HeapObject* heap_object,
                                               internal::Object* value);

        internal::Isolate* isolate_;
        internal::Object** prev_next_;
        internal::Object** prev_limit_;

        // Local::New uses CreateHandle with an Isolate* parameter.
        template<class F> friend class Local;

        // Object::GetInternalField and Context::GetEmbedderData use CreateHandle with
        // a HeapObject* in their shortcuts.
        friend class Object;
        friend class Context;
};


/**
 * A HandleScope which first allocates a handle in the current scope
 * which will be later filled with the escape value.
 */
class V8_EXPORT EscapableHandleScope : public HandleScope {
    public:
        explicit EscapableHandleScope(Isolate* isolate);
        V8_INLINE ~EscapableHandleScope() {}

        /**
         * Pushes the value into the previous scope and returns a handle to it.
         * Cannot be called twice.
         */
        template <class T>
        V8_INLINE Local<T> Escape(Local<T> value) {
            internal::Object** slot =
                Escape(reinterpret_cast<internal::Object**>(*value));
            return Local<T>(reinterpret_cast<T*>(slot));
        }

        EscapableHandleScope(const EscapableHandleScope&) = delete;
        void operator=(const EscapableHandleScope&) = delete;
        void* operator new(size_t size) = delete;
        void operator delete(void*, size_t) = delete;

    private:
        internal::Object** Escape(internal::Object** escape_value);
        internal::Object** escape_slot_;
};

class V8_EXPORT SealHandleScope {
    public:
        SealHandleScope(Isolate* isolate);
        ~SealHandleScope();

        SealHandleScope(const SealHandleScope&) = delete;
        void operator=(const SealHandleScope&) = delete;
        void* operator new(size_t size) = delete;
        void operator delete(void*, size_t) = delete;

    private:
        internal::Isolate* const isolate_;
        internal::Object** prev_limit_;
        int prev_sealed_level_;
};


// --- Special objects ---


/**
 * The superclass of values and API object templates.
 */
class V8_EXPORT Data {
    private:
        Data();
};


/**
 * The optional attributes of ScriptOrigin.
 */
class ScriptOriginOptions {
    public:
        V8_INLINE ScriptOriginOptions(bool is_embedder_debug_script = false,
                                      bool is_shared_cross_origin = false,
                                      bool is_opaque = false)
            : flags_((is_embedder_debug_script ? kIsEmbedderDebugScript : 0) |
                     (is_shared_cross_origin ? kIsSharedCrossOrigin : 0) |
                     (is_opaque ? kIsOpaque : 0)) {}
        V8_INLINE ScriptOriginOptions(int flags)
            : flags_(flags &
                     (kIsEmbedderDebugScript | kIsSharedCrossOrigin | kIsOpaque)) {}
        bool IsEmbedderDebugScript() const {
            return (flags_ & kIsEmbedderDebugScript) != 0;
        }
        bool IsSharedCrossOrigin() const {
            return (flags_ & kIsSharedCrossOrigin) != 0;
        }
        bool IsOpaque() const {
            return (flags_ & kIsOpaque) != 0;
        }
        int Flags() const {
            return flags_;
        }

    private:
        enum {
            kIsEmbedderDebugScript = 1,
            kIsSharedCrossOrigin = 1 << 1,
            kIsOpaque = 1 << 2
        };
        const int flags_;
};

/**
 * The origin, within a file, of a script.
 */
class ScriptOrigin {
    public:
        V8_INLINE ScriptOrigin(
            Local<Value> resource_name,
            Local<Integer> resource_line_offset = Local<Integer>(),
            Local<Integer> resource_column_offset = Local<Integer>(),
            Local<Boolean> resource_is_shared_cross_origin = Local<Boolean>(),
            Local<Integer> script_id = Local<Integer>(),
            Local<Boolean> resource_is_embedder_debug_script = Local<Boolean>(),
            Local<Value> source_map_url = Local<Value>(),
            Local<Boolean> resource_is_opaque = Local<Boolean>());
        V8_INLINE Local<Value> ResourceName() const;
        V8_INLINE Local<Integer> ResourceLineOffset() const;
        V8_INLINE Local<Integer> ResourceColumnOffset() const;
        /**
          * Returns true for embedder's debugger scripts
          */
        V8_INLINE Local<Integer> ScriptID() const;
        V8_INLINE Local<Value> SourceMapUrl() const;
        V8_INLINE ScriptOriginOptions Options() const {
            return options_;
        }

    private:
        Local<Value> resource_name_;
        Local<Integer> resource_line_offset_;
        Local<Integer> resource_column_offset_;
        ScriptOriginOptions options_;
        Local<Integer> script_id_;
        Local<Value> source_map_url_;
};


/**
 * A compiled JavaScript script, not yet tied to a Context.
 */
class V8_EXPORT UnboundScript {
    public:
        /**
         * Binds the script to the currently entered context.
         */
        Local<Script> BindToCurrentContext();

        int GetId();
        Local<Value> GetScriptName();

        /**
         * Data read from magic sourceURL comments.
         */
        Local<Value> GetSourceURL();
        /**
         * Data read from magic sourceMappingURL comments.
         */
        Local<Value> GetSourceMappingURL();

        /**
         * Returns zero based line number of the code_pos location in the script.
         * -1 will be returned if no information available.
         */
        int GetLineNumber(int code_pos);

        static const int kNoScriptId = 0;
};

/**
 * This is an unfinished experimental feature, and is only exposed
 * here for internal testing purposes. DO NOT USE.
 *
 * A compiled JavaScript module.
 */
class V8_EXPORT Module {
    public:
        /**
         * Returns the number of modules requested by this module.
         */
        int GetModuleRequestsLength() const;

        /**
         * Returns the ith module specifier in this module.
         * i must be < GetModuleRequestsLength() and >= 0.
         */
        Local<String> GetModuleRequest(int i) const;

        void SetEmbedderData(Local<Value> data);
        Local<Value> GetEmbedderData() const;

        typedef MaybeLocal<Module> (*ResolveCallback)(Local<Context> context,
                Local<String> specifier,
                Local<Module> referrer,
                Local<Value> data);

        /**
         * ModuleDeclarationInstantiation
         *
         * Returns false if an exception occurred during instantiation.
         */
        V8_WARN_UNUSED_RESULT bool Instantiate(
            Local<Context> context, ResolveCallback callback,
            Local<Value> callback_data = Local<Value>());

        /**
         * ModuleEvaluation
         */
        V8_WARN_UNUSED_RESULT MaybeLocal<Value> Evaluate(Local<Context> context);
};

/**
 * A compiled JavaScript script, tied to a Context which was active when the
 * script was compiled.
 */
class V8_EXPORT Script {
    public:
        /**
         * A shorthand for ScriptCompiler::Compile().
         */
        static V8_DEPRECATE_SOON(
            "Use maybe version",
            Local<Script> Compile(Local<String> source,
                                  ScriptOrigin* origin = nullptr));
        static V8_WARN_UNUSED_RESULT MaybeLocal<Script> Compile(
            Local<Context> context, Local<String> source,
            ScriptOrigin* origin = nullptr);

        static Local<Script> V8_DEPRECATE_SOON("Use maybe version",
                                               Compile(Local<String> source,
                                                       Local<String> file_name));

        /**
         * Runs the script returning the resulting value. It will be run in the
         * context in which it was created (ScriptCompiler::CompileBound or
         * UnboundScript::BindToCurrentContext()).
         */
        V8_DEPRECATE_SOON("Use maybe version", Local<Value> Run());
        V8_WARN_UNUSED_RESULT MaybeLocal<Value> Run(Local<Context> context);

        /**
         * Returns the corresponding context-unbound script.
         */
        Local<UnboundScript> GetUnboundScript();
};


/**
 * For compiling scripts.
 */
class V8_EXPORT ScriptCompiler {
    public:
        /**
         * Compilation data that the embedder can cache and pass back to speed up
         * future compilations. The data is produced if the CompilerOptions passed to
         * the compilation functions in ScriptCompiler contains produce_data_to_cache
         * = true. The data to cache can then can be retrieved from
         * UnboundScript.
         */
        struct V8_EXPORT CachedData {
            enum BufferPolicy {
                BufferNotOwned,
                BufferOwned
            };

            CachedData()
                : data(NULL),
                  length(0),
                  rejected(false),
                  buffer_policy(BufferNotOwned) {}

            // If buffer_policy is BufferNotOwned, the caller keeps the ownership of
            // data and guarantees that it stays alive until the CachedData object is
            // destroyed. If the policy is BufferOwned, the given data will be deleted
            // (with delete[]) when the CachedData object is destroyed.
            CachedData(const uint8_t* data, int length,
                       BufferPolicy buffer_policy = BufferNotOwned);
            ~CachedData();
            // TODO(marja): Async compilation; add constructors which take a callback
            // which will be called when V8 no longer needs the data.
            const uint8_t* data;
            int length;
            bool rejected;
            BufferPolicy buffer_policy;

            // Prevent copying.
            CachedData(const CachedData&) = delete;
            CachedData& operator=(const CachedData&) = delete;
        };

        /**
         * Source code which can be then compiled to a UnboundScript or Script.
         */
        class Source {
            public:
                // Source takes ownership of CachedData.
                V8_INLINE Source(Local<String> source_string, const ScriptOrigin& origin,
                                 CachedData* cached_data = NULL);
                V8_INLINE Source(Local<String> source_string,
                                 CachedData* cached_data = NULL);
                V8_INLINE ~Source();

                // Ownership of the CachedData or its buffers is *not* transferred to the
                // caller. The CachedData object is alive as long as the Source object is
                // alive.
                V8_INLINE const CachedData* GetCachedData() const;

                // Prevent copying.
                Source(const Source&) = delete;
                Source& operator=(const Source&) = delete;

            private:
                friend class ScriptCompiler;

                Local<String> source_string;

                // Origin information
                Local<Value> resource_name;
                Local<Integer> resource_line_offset;
                Local<Integer> resource_column_offset;
                ScriptOriginOptions resource_options;
                Local<Value> source_map_url;

                // Cached data from previous compilation (if a kConsume*Cache flag is
                // set), or hold newly generated cache data (kProduce*Cache flags) are
                // set when calling a compile method.
                CachedData* cached_data;
        };

        /**
         * For streaming incomplete script data to V8. The embedder should implement a
         * subclass of this class.
         */
        class V8_EXPORT ExternalSourceStream {
            public:
                virtual ~ExternalSourceStream() {}

                /**
                 * V8 calls this to request the next chunk of data from the embedder. This
                 * function will be called on a background thread, so it's OK to block and
                 * wait for the data, if the embedder doesn't have data yet. Returns the
                 * length of the data returned. When the data ends, GetMoreData should
                 * return 0. Caller takes ownership of the data.
                 *
                 * When streaming UTF-8 data, V8 handles multi-byte characters split between
                 * two data chunks, but doesn't handle multi-byte characters split between
                 * more than two data chunks. The embedder can avoid this problem by always
                 * returning at least 2 bytes of data.
                 *
                 * If the embedder wants to cancel the streaming, they should make the next
                 * GetMoreData call return 0. V8 will interpret it as end of data (and most
                 * probably, parsing will fail). The streaming task will return as soon as
                 * V8 has parsed the data it received so far.
                 */
                virtual size_t GetMoreData(const uint8_t** src) = 0;

                /**
                 * V8 calls this method to set a 'bookmark' at the current position in
                 * the source stream, for the purpose of (maybe) later calling
                 * ResetToBookmark. If ResetToBookmark is called later, then subsequent
                 * calls to GetMoreData should return the same data as they did when
                 * SetBookmark was called earlier.
                 *
                 * The embedder may return 'false' to indicate it cannot provide this
                 * functionality.
                 */
                virtual bool SetBookmark();

                /**
                 * V8 calls this to return to a previously set bookmark.
                 */
                virtual void ResetToBookmark();
        };


        /**
         * Source code which can be streamed into V8 in pieces. It will be parsed
         * while streaming. It can be compiled after the streaming is complete.
         * StreamedSource must be kept alive while the streaming task is ran (see
         * ScriptStreamingTask below).
         */
        class V8_EXPORT StreamedSource {
            public:
                enum Encoding { ONE_BYTE, TWO_BYTE, UTF8 };

                StreamedSource(ExternalSourceStream* source_stream, Encoding encoding);
                ~StreamedSource();

                // Ownership of the CachedData or its buffers is *not* transferred to the
                // caller. The CachedData object is alive as long as the StreamedSource
                // object is alive.
                const CachedData* GetCachedData() const;

                internal::StreamedSource* impl() const {
                    return impl_;
                }

                // Prevent copying.
                StreamedSource(const StreamedSource&) = delete;
                StreamedSource& operator=(const StreamedSource&) = delete;

            private:
                internal::StreamedSource* impl_;
        };

        /**
         * A streaming task which the embedder must run on a background thread to
         * stream scripts into V8. Returned by ScriptCompiler::StartStreamingScript.
         */
        class ScriptStreamingTask {
            public:
                virtual ~ScriptStreamingTask() {}
                virtual void Run() = 0;
        };

        enum CompileOptions {
            kNoCompileOptions = 0,
            kProduceParserCache,
            kConsumeParserCache,
            kProduceCodeCache,
            kConsumeCodeCache
        };

        /**
         * Compiles the specified script (context-independent).
         * Cached data as part of the source object can be optionally produced to be
         * consumed later to speed up compilation of identical source scripts.
         *
         * Note that when producing cached data, the source must point to NULL for
         * cached data. When consuming cached data, the cached data must have been
         * produced by the same version of V8.
         *
         * \param source Script source code.
         * \return Compiled script object (context independent; for running it must be
         *   bound to a context).
         */
        static V8_DEPRECATED("Use maybe version",
                             Local<UnboundScript> CompileUnbound(
                                 Isolate* isolate, Source* source,
                                 CompileOptions options = kNoCompileOptions));
        static V8_WARN_UNUSED_RESULT MaybeLocal<UnboundScript> CompileUnboundScript(
            Isolate* isolate, Source* source,
            CompileOptions options = kNoCompileOptions);

        /**
         * Compiles the specified script (bound to current context).
         *
         * \param source Script source code.
         * \param pre_data Pre-parsing data, as obtained by ScriptData::PreCompile()
         *   using pre_data speeds compilation if it's done multiple times.
         *   Owned by caller, no references are kept when this function returns.
         * \return Compiled script object, bound to the context that was active
         *   when this function was called. When run it will always use this
         *   context.
         */
        static V8_DEPRECATED(
            "Use maybe version",
            Local<Script> Compile(Isolate* isolate, Source* source,
                                  CompileOptions options = kNoCompileOptions));
        static V8_WARN_UNUSED_RESULT MaybeLocal<Script> Compile(
            Local<Context> context, Source* source,
            CompileOptions options = kNoCompileOptions);

        /**
         * Returns a task which streams script data into V8, or NULL if the script
         * cannot be streamed. The user is responsible for running the task on a
         * background thread and deleting it. When ran, the task starts parsing the
         * script, and it will request data from the StreamedSource as needed. When
         * ScriptStreamingTask::Run exits, all data has been streamed and the script
         * can be compiled (see Compile below).
         *
         * This API allows to start the streaming with as little data as possible, and
         * the remaining data (for example, the ScriptOrigin) is passed to Compile.
         */
        static ScriptStreamingTask* StartStreamingScript(
            Isolate* isolate, StreamedSource* source,
            CompileOptions options = kNoCompileOptions);

        /**
         * Compiles a streamed script (bound to current context).
         *
         * This can only be called after the streaming has finished
         * (ScriptStreamingTask has been run). V8 doesn't construct the source string
         * during streaming, so the embedder needs to pass the full source here.
         */
        static V8_DEPRECATED("Use maybe version",
                             Local<Script> Compile(Isolate* isolate,
                                     StreamedSource* source,
                                     Local<String> full_source_string,
                                     const ScriptOrigin& origin));
        static V8_WARN_UNUSED_RESULT MaybeLocal<Script> Compile(
            Local<Context> context, StreamedSource* source,
            Local<String> full_source_string, const ScriptOrigin& origin);

        /**
         * Return a version tag for CachedData for the current V8 version & flags.
         *
         * This value is meant only for determining whether a previously generated
         * CachedData instance is still valid; the tag has no other meaing.
         *
         * Background: The data carried by CachedData may depend on the exact
         *   V8 version number or currently compiler flags. This means when
         *   persisting CachedData, the embedder must take care to not pass in
         *   data from another V8 version, or the same version with different
         *   features enabled.
         *
         *   The easiest way to do so is to clear the embedder's cache on any
         *   such change.
         *
         *   Alternatively, this tag can be stored alongside the cached data and
         *   compared when it is being used.
         */
        static uint32_t CachedDataVersionTag();

        /**
         * This is an unfinished experimental feature, and is only exposed
         * here for internal testing purposes. DO NOT USE.
         *
         * Compile an ES module, returning a Module that encapsulates
         * the compiled code.
         *
         * Corresponds to the ParseModule abstract operation in the
         * ECMAScript specification.
         */
        static V8_WARN_UNUSED_RESULT MaybeLocal<Module> CompileModule(
            Isolate* isolate, Source* source);

        /**
         * Compile a function for a given context. This is equivalent to running
         *
         * with (obj) {
         *   return function(args) { ... }
         * }
         *
         * It is possible to specify multiple context extensions (obj in the above
         * example).
         */
        static V8_DEPRECATE_SOON("Use maybe version",
                                 Local<Function> CompileFunctionInContext(
                                     Isolate* isolate, Source* source,
                                     Local<Context> context, size_t arguments_count,
                                     Local<String> arguments[],
                                     size_t context_extension_count,
                                     Local<Object> context_extensions[]));
        static V8_WARN_UNUSED_RESULT MaybeLocal<Function> CompileFunctionInContext(
            Local<Context> context, Source* source, size_t arguments_count,
            Local<String> arguments[], size_t context_extension_count,
            Local<Object> context_extensions[]);

    private:
        static V8_WARN_UNUSED_RESULT MaybeLocal<UnboundScript> CompileUnboundInternal(
            Isolate* isolate, Source* source, CompileOptions options, bool is_module);
};


/**
 * An error message.
 */
class V8_EXPORT Message {
    public:
        Local<String> Get() const;

        V8_DEPRECATE_SOON("Use maybe version", Local<String> GetSourceLine() const);
        V8_WARN_UNUSED_RESULT MaybeLocal<String> GetSourceLine(
            Local<Context> context) const;

        /**
         * Returns the origin for the script from where the function causing the
         * error originates.
         */
        ScriptOrigin GetScriptOrigin() const;

        /**
         * Returns the resource name for the script from where the function causing
         * the error originates.
         */
        Local<Value> GetScriptResourceName() const;

        /**
         * Exception stack trace. By default stack traces are not captured for
         * uncaught exceptions. SetCaptureStackTraceForUncaughtExceptions allows
         * to change this option.
         */
        Local<StackTrace> GetStackTrace() const;

        /**
         * Returns the number, 1-based, of the line where the error occurred.
         */
        V8_DEPRECATE_SOON("Use maybe version", int GetLineNumber() const);
        V8_WARN_UNUSED_RESULT Maybe<int> GetLineNumber(Local<Context> context) const;

        /**
         * Returns the index within the script of the first character where
         * the error occurred.
         */
        int GetStartPosition() const;

        /**
         * Returns the index within the script of the last character where
         * the error occurred.
         */
        int GetEndPosition() const;

        /**
         * Returns the index within the line of the first character where
         * the error occurred.
         */
        V8_DEPRECATE_SOON("Use maybe version", int GetStartColumn() const);
        V8_WARN_UNUSED_RESULT Maybe<int> GetStartColumn(Local<Context> context) const;

        /**
         * Returns the index within the line of the last character where
         * the error occurred.
         */
        V8_DEPRECATED("Use maybe version", int GetEndColumn() const);
        V8_WARN_UNUSED_RESULT Maybe<int> GetEndColumn(Local<Context> context) const;

        /**
         * Passes on the value set by the embedder when it fed the script from which
         * this Message was generated to V8.
         */
        bool IsSharedCrossOrigin() const;
        bool IsOpaque() const;

        // TODO(1245381): Print to a string instead of on a FILE.
        static void PrintCurrentStackTrace(Isolate* isolate, FILE* out);

        static const int kNoLineNumberInfo = 0;
        static const int kNoColumnInfo = 0;
        static const int kNoScriptIdInfo = 0;
};


/**
 * Representation of a JavaScript stack trace. The information collected is a
 * snapshot of the execution stack and the information remains valid after
 * execution continues.
 */
class V8_EXPORT StackTrace {
    public:
        /**
         * Flags that determine what information is placed captured for each
         * StackFrame when grabbing the current stack trace.
         */
        enum StackTraceOptions {
            kLineNumber = 1,
            kColumnOffset = 1 << 1 | kLineNumber,
            kScriptName = 1 << 2,
            kFunctionName = 1 << 3,
            kIsEval = 1 << 4,
            kIsConstructor = 1 << 5,
            kScriptNameOrSourceURL = 1 << 6,
            kScriptId = 1 << 7,
            kExposeFramesAcrossSecurityOrigins = 1 << 8,
            kOverview = kLineNumber | kColumnOffset | kScriptName | kFunctionName,
            kDetailed = kOverview | kIsEval | kIsConstructor | kScriptNameOrSourceURL
        };

        /**
         * Returns a StackFrame at a particular index.
         */
        Local<StackFrame> GetFrame(uint32_t index) const;

        /**
         * Returns the number of StackFrames.
         */
        int GetFrameCount() const;

        /**
         * Returns StackTrace as a v8::Array that contains StackFrame objects.
         */
        Local<Array> AsArray();

        /**
         * Grab a snapshot of the current JavaScript execution stack.
         *
         * \param frame_limit The maximum number of stack frames we want to capture.
         * \param options Enumerates the set of things we will capture for each
         *   StackFrame.
         */
        static Local<StackTrace> CurrentStackTrace(
            Isolate* isolate,
            int frame_limit,
            StackTraceOptions options = kOverview);
};


/**
 * A single JavaScript stack frame.
 */
class V8_EXPORT StackFrame {
    public:
        /**
         * Returns the number, 1-based, of the line for the associate function call.
         * This method will return Message::kNoLineNumberInfo if it is unable to
         * retrieve the line number, or if kLineNumber was not passed as an option
         * when capturing the StackTrace.
         */
        int GetLineNumber() const;

        /**
         * Returns the 1-based column offset on the line for the associated function
         * call.
         * This method will return Message::kNoColumnInfo if it is unable to retrieve
         * the column number, or if kColumnOffset was not passed as an option when
         * capturing the StackTrace.
         */
        int GetColumn() const;

        /**
         * Returns the id of the script for the function for this StackFrame.
         * This method will return Message::kNoScriptIdInfo if it is unable to
         * retrieve the script id, or if kScriptId was not passed as an option when
         * capturing the StackTrace.
         */
        int GetScriptId() const;

        /**
         * Returns the name of the resource that contains the script for the
         * function for this StackFrame.
         */
        Local<String> GetScriptName() const;

        /**
         * Returns the name of the resource that contains the script for the
         * function for this StackFrame or sourceURL value if the script name
         * is undefined and its source ends with //# sourceURL=... string or
         * deprecated //@ sourceURL=... string.
         */
        Local<String> GetScriptNameOrSourceURL() const;

        /**
         * Returns the name of the function associated with this stack frame.
         */
        Local<String> GetFunctionName() const;

        /**
         * Returns whether or not the associated function is compiled via a call to
         * eval().
         */
        bool IsEval() const;

        /**
         * Returns whether or not the associated function is called as a
         * constructor via "new".
         */
        bool IsConstructor() const;
};


// A StateTag represents a possible state of the VM.
enum StateTag { JS, GC, COMPILER, OTHER, EXTERNAL, IDLE };

// A RegisterState represents the current state of registers used
// by the sampling profiler API.
struct RegisterState {
    RegisterState() : pc(nullptr), sp(nullptr), fp(nullptr) {}
    void* pc;  // Instruction pointer.
    void* sp;  // Stack pointer.
    void* fp;  // Frame pointer.
};

// The output structure filled up by GetStackSample API function.
struct SampleInfo {
    size_t frames_count;            // Number of frames collected.
    StateTag vm_state;              // Current VM state.
    void* external_callback_entry;  // External callback address if VM is
    // executing an external callback.
};

/**
 * A JSON Parser and Stringifier.
 */
class V8_EXPORT JSON {
    public:
        /**
         * Tries to parse the string |json_string| and returns it as value if
         * successful.
         *
         * \param json_string The string to parse.
         * \return The corresponding value if successfully parsed.
         */
        static V8_DEPRECATED("Use the maybe version taking context",
                             Local<Value> Parse(Local<String> json_string));
        static V8_DEPRECATE_SOON("Use the maybe version taking context",
                                 MaybeLocal<Value> Parse(Isolate* isolate,
                                         Local<String> json_string));
        static V8_WARN_UNUSED_RESULT MaybeLocal<Value> Parse(
            Local<Context> context, Local<String> json_string);

        /**
         * Tries to stringify the JSON-serializable object |json_object| and returns
         * it as string if successful.
         *
         * \param json_object The JSON-serializable object to stringify.
         * \return The corresponding string if successfully stringified.
         */
        static V8_WARN_UNUSED_RESULT MaybeLocal<String> Stringify(
            Local<Context> context, Local<Object> json_object,
            Local<String> gap = Local<String>());
};

/**
 * Value serialization compatible with the HTML structured clone algorithm.
 * The format is backward-compatible (i.e. safe to store to disk).
 *
 * WARNING: This API is under development, and changes (including incompatible
 * changes to the API or wire format) may occur without notice until this
 * warning is removed.
 */
class V8_EXPORT ValueSerializer {
    public:
        class V8_EXPORT Delegate {
            public:
                virtual ~Delegate() {}

                /*
                 * Handles the case where a DataCloneError would be thrown in the structured
                 * clone spec. Other V8 embedders may throw some other appropriate exception
                 * type.
                 */
                virtual void ThrowDataCloneError(Local<String> message) = 0;

                /*
                 * The embedder overrides this method to write some kind of host object, if
                 * possible. If not, a suitable exception should be thrown and
                 * Nothing<bool>() returned.
                 */
                virtual Maybe<bool> WriteHostObject(Isolate* isolate, Local<Object> object);
        };

        explicit ValueSerializer(Isolate* isolate);
        ValueSerializer(Isolate* isolate, Delegate* delegate);
        ~ValueSerializer();

        /*
         * Writes out a header, which includes the format version.
         */
        void WriteHeader();

        /*
         * Serializes a JavaScript value into the buffer.
         */
        V8_WARN_UNUSED_RESULT Maybe<bool> WriteValue(Local<Context> context,
                Local<Value> value);

        /*
         * Returns the stored data. This serializer should not be used once the buffer
         * is released. The contents are undefined if a previous write has failed.
         */
        std::vector<uint8_t> ReleaseBuffer();

        /*
         * Marks an ArrayBuffer as havings its contents transferred out of band.
         * Pass the corresponding JSArrayBuffer in the deserializing context to
         * ValueDeserializer::TransferArrayBuffer.
         */
        void TransferArrayBuffer(uint32_t transfer_id,
                                 Local<ArrayBuffer> array_buffer);

        /*
         * Similar to TransferArrayBuffer, but for SharedArrayBuffer.
         */
        void TransferSharedArrayBuffer(uint32_t transfer_id,
                                       Local<SharedArrayBuffer> shared_array_buffer);

        /*
         * Write raw data in various common formats to the buffer.
         * Note that integer types are written in base-128 varint format, not with a
         * binary copy. For use during an override of Delegate::WriteHostObject.
         */
        void WriteUint32(uint32_t value);
        void WriteUint64(uint64_t value);
        void WriteDouble(double value);
        void WriteRawBytes(const void* source, size_t length);

    private:
        ValueSerializer(const ValueSerializer&) = delete;
        void operator=(const ValueSerializer&) = delete;

        struct PrivateData;
        PrivateData* private_;
};

/**
 * Deserializes values from data written with ValueSerializer, or a compatible
 * implementation.
 *
 * WARNING: This API is under development, and changes (including incompatible
 * changes to the API or wire format) may occur without notice until this
 * warning is removed.
 */
class V8_EXPORT ValueDeserializer {
    public:
        class V8_EXPORT Delegate {
            public:
                virtual ~Delegate() {}

                /*
                 * The embedder overrides this method to read some kind of host object, if
                 * possible. If not, a suitable exception should be thrown and
                 * MaybeLocal<Object>() returned.
                 */
                virtual MaybeLocal<Object> ReadHostObject(Isolate* isolate);
        };

        ValueDeserializer(Isolate* isolate, const uint8_t* data, size_t size);
        ValueDeserializer(Isolate* isolate, const uint8_t* data, size_t size,
                          Delegate* delegate);
        ~ValueDeserializer();

        /*
         * Reads and validates a header (including the format version).
         * May, for example, reject an invalid or unsupported wire format.
         */
        V8_WARN_UNUSED_RESULT Maybe<bool> ReadHeader(Local<Context> context);
        V8_DEPRECATE_SOON("Use Local<Context> version", Maybe<bool> ReadHeader());

        /*
         * Deserializes a JavaScript value from the buffer.
         */
        V8_WARN_UNUSED_RESULT MaybeLocal<Value> ReadValue(Local<Context> context);

        /*
         * Accepts the array buffer corresponding to the one passed previously to
         * ValueSerializer::TransferArrayBuffer.
         */
        void TransferArrayBuffer(uint32_t transfer_id,
                                 Local<ArrayBuffer> array_buffer);

        /*
         * Similar to TransferArrayBuffer, but for SharedArrayBuffer.
         * transfer_id exists in the same namespace as unshared ArrayBuffer objects.
         */
        void TransferSharedArrayBuffer(uint32_t transfer_id,
                                       Local<SharedArrayBuffer> shared_array_buffer);

        /*
         * Must be called before ReadHeader to enable support for reading the legacy
         * wire format (i.e., which predates this being shipped).
         *
         * Don't use this unless you need to read data written by previous versions of
         * blink::ScriptValueSerializer.
         */
        void SetSupportsLegacyWireFormat(bool supports_legacy_wire_format);

        /*
         * Reads the underlying wire format version. Likely mostly to be useful to
         * legacy code reading old wire format versions. Must be called after
         * ReadHeader.
         */
        uint32_t GetWireFormatVersion() const;

        /*
         * Reads raw data in various common formats to the buffer.
         * Note that integer types are read in base-128 varint format, not with a
         * binary copy. For use during an override of Delegate::ReadHostObject.
         */
        V8_WARN_UNUSED_RESULT bool ReadUint32(uint32_t* value);
        V8_WARN_UNUSED_RESULT bool ReadUint64(uint64_t* value);
        V8_WARN_UNUSED_RESULT bool ReadDouble(double* value);
        V8_WARN_UNUSED_RESULT bool ReadRawBytes(size_t length, const void** data);

    private:
        ValueDeserializer(const ValueDeserializer&) = delete;
        void operator=(const ValueDeserializer&) = delete;

        struct PrivateData;
        PrivateData* private_;
};

/**
 * A map whose keys are referenced weakly. It is similar to JavaScript WeakMap
 * but can be created without entering a v8::Context and hence shouldn't
 * escape to JavaScript.
 */
class V8_EXPORT NativeWeakMap : public Data {
    public:
        static Local<NativeWeakMap> New(Isolate* isolate);
        void Set(Local<Value> key, Local<Value> value);
        Local<Value> Get(Local<Value> key);
        bool Has(Local<Value> key);
        bool Delete(Local<Value> key);
};


// --- Value ---


/**
 * The superclass of all JavaScript values and objects.
 */
class V8_EXPORT Value : public Data {
    public:
        /**
         * Returns true if this value is the undefined value.  See ECMA-262
         * 4.3.10.
         */
        V8_INLINE bool IsUndefined() const;

        /**
         * Returns true if this value is the null value.  See ECMA-262
         * 4.3.11.
         */
        V8_INLINE bool IsNull() const;

        /**
        * Returns true if this value is true.
        */
        bool IsTrue() const;

        /**
         * Returns true if this value is false.
         */
        bool IsFalse() const;

        /**
         * Returns true if this value is a symbol or a string.
         * This is an experimental feature.
         */
        bool IsName() const;

        /**
         * Returns true if this value is an instance of the String type.
         * See ECMA-262 8.4.
         */
        V8_INLINE bool IsString() const;

        /**
         * Returns true if this value is a symbol.
         * This is an experimental feature.
         */
        bool IsSymbol() const;

        /**
         * Returns true if this value is a function.
         */
        bool IsFunction() const;

        /**
         * Returns true if this value is an array. Note that it will return false for
         * an Proxy for an array.
         */
        bool IsArray() const;

        /**
         * Returns true if this value is an object.
         */
        bool IsObject() const;

        /**
         * Returns true if this value is boolean.
         */
        bool IsBoolean() const;

        /**
         * Returns true if this value is a number.
         */
        bool IsNumber() const;

        /**
         * Returns true if this value is external.
         */
        bool IsExternal() const;

        /**
         * Returns true if this value is a 32-bit signed integer.
         */
        bool IsInt32() const;

        /**
         * Returns true if this value is a 32-bit unsigned integer.
         */
        bool IsUint32() const;

        /**
         * Returns true if this value is a Date.
         */
        bool IsDate() const;

        /**
         * Returns true if this value is an Arguments object.
         */
        bool IsArgumentsObject() const;

        /**
         * Returns true if this value is a Boolean object.
         */
        bool IsBooleanObject() const;

        /**
         * Returns true if this value is a Number object.
         */
        bool IsNumberObject() const;

        /**
         * Returns true if this value is a String object.
         */
        bool IsStringObject() const;

        /**
         * Returns true if this value is a Symbol object.
         * This is an experimental feature.
         */
        bool IsSymbolObject() const;

        /**
         * Returns true if this value is a NativeError.
         */
        bool IsNativeError() const;

        /**
         * Returns true if this value is a RegExp.
         */
        bool IsRegExp() const;

        /**
         * Returns true if this value is an async function.
         */
        bool IsAsyncFunction() const;

        /**
         * Returns true if this value is a Generator function.
         * This is an experimental feature.
         */
        bool IsGeneratorFunction() const;

        /**
         * Returns true if this value is a Generator object (iterator).
         * This is an experimental feature.
         */
        bool IsGeneratorObject() const;

        /**
         * Returns true if this value is a Promise.
         * This is an experimental feature.
         */
        bool IsPromise() const;

        /**
         * Returns true if this value is a Map.
         */
        bool IsMap() const;

        /**
         * Returns true if this value is a Set.
         */
        bool IsSet() const;

        /**
         * Returns true if this value is a Map Iterator.
         */
        bool IsMapIterator() const;

        /**
         * Returns true if this value is a Set Iterator.
         */
        bool IsSetIterator() const;

        /**
         * Returns true if this value is a WeakMap.
         */
        bool IsWeakMap() const;

        /**
         * Returns true if this value is a WeakSet.
         */
        bool IsWeakSet() const;

        /**
         * Returns true if this value is an ArrayBuffer.
         * This is an experimental feature.
         */
        bool IsArrayBuffer() const;

        /**
         * Returns true if this value is an ArrayBufferView.
         * This is an experimental feature.
         */
        bool IsArrayBufferView() const;

        /**
         * Returns true if this value is one of TypedArrays.
         * This is an experimental feature.
         */
        bool IsTypedArray() const;

        /**
         * Returns true if this value is an Uint8Array.
         * This is an experimental feature.
         */
        bool IsUint8Array() const;

        /**
         * Returns true if this value is an Uint8ClampedArray.
         * This is an experimental feature.
         */
        bool IsUint8ClampedArray() const;

        /**
         * Returns true if this value is an Int8Array.
         * This is an experimental feature.
         */
        bool IsInt8Array() const;

        /**
         * Returns true if this value is an Uint16Array.
         * This is an experimental feature.
         */
        bool IsUint16Array() const;

        /**
         * Returns true if this value is an Int16Array.
         * This is an experimental feature.
         */
        bool IsInt16Array() const;

        /**
         * Returns true if this value is an Uint32Array.
         * This is an experimental feature.
         */
        bool IsUint32Array() const;

        /**
         * Returns true if this value is an Int32Array.
         * This is an experimental feature.
         */
        bool IsInt32Array() const;

        /**
         * Returns true if this value is a Float32Array.
         * This is an experimental feature.
         */
        bool IsFloat32Array() const;

        /**
         * Returns true if this value is a Float64Array.
         * This is an experimental feature.
         */
        bool IsFloat64Array() const;

        /**
         * Returns true if this value is a SIMD Float32x4.
         * This is an experimental feature.
         */
        bool IsFloat32x4() const;

        /**
         * Returns true if this value is a DataView.
         * This is an experimental feature.
         */
        bool IsDataView() const;

        /**
         * Returns true if this value is a SharedArrayBuffer.
         * This is an experimental feature.
         */
        bool IsSharedArrayBuffer() const;

        /**
         * Returns true if this value is a JavaScript Proxy.
         */
        bool IsProxy() const;

        bool IsWebAssemblyCompiledModule() const;

        V8_WARN_UNUSED_RESULT MaybeLocal<Boolean> ToBoolean(
            Local<Context> context) const;
        V8_WARN_UNUSED_RESULT MaybeLocal<Number> ToNumber(
            Local<Context> context) const;
        V8_WARN_UNUSED_RESULT MaybeLocal<String> ToString(
            Local<Context> context) const;
        V8_WARN_UNUSED_RESULT MaybeLocal<String> ToDetailString(
            Local<Context> context) const;
        V8_WARN_UNUSED_RESULT MaybeLocal<Object> ToObject(
            Local<Context> context) const;
        V8_WARN_UNUSED_RESULT MaybeLocal<Integer> ToInteger(
            Local<Context> context) const;
        V8_WARN_UNUSED_RESULT MaybeLocal<Uint32> ToUint32(
            Local<Context> context) const;
        V8_WARN_UNUSED_RESULT MaybeLocal<Int32> ToInt32(Local<Context> context) const;

        V8_DEPRECATE_SOON("Use maybe version",
                          Local<Boolean> ToBoolean(Isolate* isolate) const);
        V8_DEPRECATE_SOON("Use maybe version",
                          Local<Number> ToNumber(Isolate* isolate) const);
        V8_DEPRECATE_SOON("Use maybe version",
                          Local<String> ToString(Isolate* isolate) const);
        V8_DEPRECATED("Use maybe version",
                      Local<String> ToDetailString(Isolate* isolate) const);
        V8_DEPRECATE_SOON("Use maybe version",
                          Local<Object> ToObject(Isolate* isolate) const);
        V8_DEPRECATE_SOON("Use maybe version",
                          Local<Integer> ToInteger(Isolate* isolate) const);
        V8_DEPRECATED("Use maybe version",
                      Local<Uint32> ToUint32(Isolate* isolate) const);
        V8_DEPRECATE_SOON("Use maybe version",
                          Local<Int32> ToInt32(Isolate* isolate) const);

        inline V8_DEPRECATE_SOON("Use maybe version",
                                 Local<Boolean> ToBoolean() const);
        inline V8_DEPRECATED("Use maybe version", Local<Number> ToNumber() const);
        inline V8_DEPRECATE_SOON("Use maybe version", Local<String> ToString() const);
        inline V8_DEPRECATED("Use maybe version",
                             Local<String> ToDetailString() const);
        inline V8_DEPRECATE_SOON("Use maybe version", Local<Object> ToObject() const);
        inline V8_DEPRECATE_SOON("Use maybe version",
                                 Local<Integer> ToInteger() const);
        inline V8_DEPRECATED("Use maybe version", Local<Uint32> ToUint32() const);
        inline V8_DEPRECATED("Use maybe version", Local<Int32> ToInt32() const);

        /**
         * Attempts to convert a string to an array index.
         * Returns an empty handle if the conversion fails.
         */
        V8_DEPRECATED("Use maybe version", Local<Uint32> ToArrayIndex() const);
        V8_WARN_UNUSED_RESULT MaybeLocal<Uint32> ToArrayIndex(
            Local<Context> context) const;

        V8_WARN_UNUSED_RESULT Maybe<bool> BooleanValue(Local<Context> context) const;
        V8_WARN_UNUSED_RESULT Maybe<double> NumberValue(Local<Context> context) const;
        V8_WARN_UNUSED_RESULT Maybe<int64_t> IntegerValue(
            Local<Context> context) const;
        V8_WARN_UNUSED_RESULT Maybe<uint32_t> Uint32Value(
            Local<Context> context) const;
        V8_WARN_UNUSED_RESULT Maybe<int32_t> Int32Value(Local<Context> context) const;

        V8_DEPRECATE_SOON("Use maybe version", bool BooleanValue() const);
        V8_DEPRECATE_SOON("Use maybe version", double NumberValue() const);
        V8_DEPRECATE_SOON("Use maybe version", int64_t IntegerValue() const);
        V8_DEPRECATE_SOON("Use maybe version", uint32_t Uint32Value() const);
        V8_DEPRECATE_SOON("Use maybe version", int32_t Int32Value() const);

        /** JS == */
        V8_DEPRECATE_SOON("Use maybe version", bool Equals(Local<Value> that) const);
        V8_WARN_UNUSED_RESULT Maybe<bool> Equals(Local<Context> context,
                Local<Value> that) const;
        bool StrictEquals(Local<Value> that) const;
        bool SameValue(Local<Value> that) const;

        template <class T> V8_INLINE static Value* Cast(T* value);

        Local<String> TypeOf(v8::Isolate*);

    private:
        V8_INLINE bool QuickIsUndefined() const;
        V8_INLINE bool QuickIsNull() const;
        V8_INLINE bool QuickIsString() const;
        bool FullIsUndefined() const;
        bool FullIsNull() const;
        bool FullIsString() const;
};


/**
 * The superclass of primitive values.  See ECMA-262 4.3.2.
 */
class V8_EXPORT Primitive : public Value { };


/**
 * A primitive boolean value (ECMA-262, 4.3.14).  Either the true
 * or false value.
 */
class V8_EXPORT Boolean : public Primitive {
    public:
        bool Value() const;
        V8_INLINE static Boolean* Cast(v8::Value* obj);
        V8_INLINE static Local<Boolean> New(Isolate* isolate, bool value);

    private:
        static void CheckCast(v8::Value* obj);
};


/**
 * A superclass for symbols and strings.
 */
class V8_EXPORT Name : public Primitive {
    public:
        /**
         * Returns the identity hash for this object. The current implementation
         * uses an inline property on the object to store the identity hash.
         *
         * The return value will never be 0. Also, it is not guaranteed to be
         * unique.
         */
        int GetIdentityHash();

        V8_INLINE static Name* Cast(v8::Value* obj);
    private:
        static void CheckCast(v8::Value* obj);
};


enum class NewStringType { kNormal, kInternalized };


/**
 * A JavaScript string value (ECMA-262, 4.3.17).
 */
class V8_EXPORT String : public Name {
    public:
        static const int kMaxLength = (1 << 28) - 16;

        enum Encoding {
            UNKNOWN_ENCODING = 0x1,
            TWO_BYTE_ENCODING = 0x0,
            ONE_BYTE_ENCODING = 0x4
        };
        /**
         * Returns the number of characters in this string.
         */
        int Length() const;

        /**
         * Returns the number of bytes in the UTF-8 encoded
         * representation of this string.
         */
        int Utf8Length() const;

        /**
         * Returns whether this string is known to contain only one byte data.
         * Does not read the string.
         * False negatives are possible.
         */
        bool IsOneByte() const;

        /**
         * Returns whether this string contain only one byte data.
         * Will read the entire string in some cases.
         */
        bool ContainsOnlyOneByte() const;

        /**
         * Write the contents of the string to an external buffer.
         * If no arguments are given, expects the buffer to be large
         * enough to hold the entire string and NULL terminator. Copies
         * the contents of the string and the NULL terminator into the
         * buffer.
         *
         * WriteUtf8 will not write partial UTF-8 sequences, preferring to stop
         * before the end of the buffer.
         *
         * Copies up to length characters into the output buffer.
         * Only null-terminates if there is enough space in the buffer.
         *
         * \param buffer The buffer into which the string will be copied.
         * \param start The starting position within the string at which
         * copying begins.
         * \param length The number of characters to copy from the string.  For
         *    WriteUtf8 the number of bytes in the buffer.
         * \param nchars_ref The number of characters written, can be NULL.
         * \param options Various options that might affect performance of this or
         *    subsequent operations.
         * \return The number of characters copied to the buffer excluding the null
         *    terminator.  For WriteUtf8: The number of bytes copied to the buffer
         *    including the null terminator (if written).
         */
        enum WriteOptions {
            NO_OPTIONS = 0,
            HINT_MANY_WRITES_EXPECTED = 1,
            NO_NULL_TERMINATION = 2,
            PRESERVE_ONE_BYTE_NULL = 4,
            // Used by WriteUtf8 to replace orphan surrogate code units with the
            // unicode replacement character. Needs to be set to guarantee valid UTF-8
            // output.
            REPLACE_INVALID_UTF8 = 8
        };

        // 16-bit character codes.
        int Write(uint16_t* buffer,
                  int start = 0,
                  int length = -1,
                  int options = NO_OPTIONS) const;
        // One byte characters.
        int WriteOneByte(uint8_t* buffer,
                         int start = 0,
                         int length = -1,
                         int options = NO_OPTIONS) const;
        // UTF-8 encoded characters.
        int WriteUtf8(char* buffer,
                      int length = -1,
                      int* nchars_ref = NULL,
                      int options = NO_OPTIONS) const;

        /**
         * A zero length string.
         */
        V8_INLINE static v8::Local<v8::String> Empty(Isolate* isolate);

        /**
         * Returns true if the string is external
         */
        bool IsExternal() const;

        /**
         * Returns true if the string is both external and one-byte.
         */
        bool IsExternalOneByte() const;

        class V8_EXPORT ExternalStringResourceBase {  // NOLINT
            public:
                virtual ~ExternalStringResourceBase() {}

                virtual bool IsCompressible() const {
                    return false;
                }

            protected:
                ExternalStringResourceBase() {}

                /**
                 * Internally V8 will call this Dispose method when the external string
                 * resource is no longer needed. The default implementation will use the
                 * delete operator. This method can be overridden in subclasses to
                 * control how allocated external string resources are disposed.
                 */
                virtual void Dispose() {
                    delete this;
                }

                // Disallow copying and assigning.
                ExternalStringResourceBase(const ExternalStringResourceBase&) = delete;
                void operator=(const ExternalStringResourceBase&) = delete;

            private:
                friend class v8::internal::Heap;
        };

        /**
         * An ExternalStringResource is a wrapper around a two-byte string
         * buffer that resides outside V8's heap. Implement an
         * ExternalStringResource to manage the life cycle of the underlying
         * buffer.  Note that the string data must be immutable.
         */
        class V8_EXPORT ExternalStringResource
            : public ExternalStringResourceBase {
            public:
                /**
                 * Override the destructor to manage the life cycle of the underlying
                 * buffer.
                 */
                virtual ~ExternalStringResource() {}

                /**
                 * The string data from the underlying buffer.
                 */
                virtual const uint16_t* data() const = 0;

                /**
                 * The length of the string. That is, the number of two-byte characters.
                 */
                virtual size_t length() const = 0;

            protected:
                ExternalStringResource() {}
        };

        /**
         * An ExternalOneByteStringResource is a wrapper around an one-byte
         * string buffer that resides outside V8's heap. Implement an
         * ExternalOneByteStringResource to manage the life cycle of the
         * underlying buffer.  Note that the string data must be immutable
         * and that the data must be Latin-1 and not UTF-8, which would require
         * special treatment internally in the engine and do not allow efficient
         * indexing.  Use String::New or convert to 16 bit data for non-Latin1.
         */

        class V8_EXPORT ExternalOneByteStringResource
            : public ExternalStringResourceBase {
            public:
                /**
                 * Override the destructor to manage the life cycle of the underlying
                 * buffer.
                 */
                virtual ~ExternalOneByteStringResource() {}
                /** The string data from the underlying buffer.*/
                virtual const char* data() const = 0;
                /** The number of Latin-1 characters in the string.*/
                virtual size_t length() const = 0;
            protected:
                ExternalOneByteStringResource() {}
        };

        /**
         * If the string is an external string, return the ExternalStringResourceBase
         * regardless of the encoding, otherwise return NULL.  The encoding of the
         * string is returned in encoding_out.
         */
        V8_INLINE ExternalStringResourceBase* GetExternalStringResourceBase(
            Encoding* encoding_out) const;

        /**
         * Get the ExternalStringResource for an external string.  Returns
         * NULL if IsExternal() doesn't return true.
         */
        V8_INLINE ExternalStringResource* GetExternalStringResource() const;

        /**
         * Get the ExternalOneByteStringResource for an external one-byte string.
         * Returns NULL if IsExternalOneByte() doesn't return true.
         */
        const ExternalOneByteStringResource* GetExternalOneByteStringResource() const;

        V8_INLINE static String* Cast(v8::Value* obj);

        // TODO(dcarney): remove with deprecation of New functions.
        enum NewStringType {
            kNormalString = static_cast<int>(v8::NewStringType::kNormal),
            kInternalizedString = static_cast<int>(v8::NewStringType::kInternalized)
        };

        /** Allocates a new string from UTF-8 data.*/
        static V8_DEPRECATE_SOON(
            "Use maybe version",
            Local<String> NewFromUtf8(Isolate* isolate, const char* data,
                                      NewStringType type = kNormalString,
                                      int length = -1));

        /** Allocates a new string from UTF-8 data. Only returns an empty value when
         * length > kMaxLength. **/
        static V8_WARN_UNUSED_RESULT MaybeLocal<String> NewFromUtf8(
            Isolate* isolate, const char* data, v8::NewStringType type,
            int length = -1);

        /** Allocates a new string from Latin-1 data.*/
        static V8_DEPRECATED(
            "Use maybe version",
            Local<String> NewFromOneByte(Isolate* isolate, const uint8_t* data,
                                         NewStringType type = kNormalString,
                                         int length = -1));

        /** Allocates a new string from Latin-1 data.  Only returns an empty value
         * when length > kMaxLength. **/
        static V8_WARN_UNUSED_RESULT MaybeLocal<String> NewFromOneByte(
            Isolate* isolate, const uint8_t* data, v8::NewStringType type,
            int length = -1);

        /** Allocates a new string from UTF-16 data.*/
        static V8_DEPRECATE_SOON(
            "Use maybe version",
            Local<String> NewFromTwoByte(Isolate* isolate, const uint16_t* data,
                                         NewStringType type = kNormalString,
                                         int length = -1));

        /** Allocates a new string from UTF-16 data. Only returns an empty value when
         * length > kMaxLength. **/
        static V8_WARN_UNUSED_RESULT MaybeLocal<String> NewFromTwoByte(
            Isolate* isolate, const uint16_t* data, v8::NewStringType type,
            int length = -1);

        /**
         * Creates a new string by concatenating the left and the right strings
         * passed in as parameters.
         */
        static Local<String> Concat(Local<String> left, Local<String> right);

        /**
         * Creates a new external string using the data defined in the given
         * resource. When the external string is no longer live on V8's heap the
         * resource will be disposed by calling its Dispose method. The caller of
         * this function should not otherwise delete or modify the resource. Neither
         * should the underlying buffer be deallocated or modified except through the
         * destructor of the external string resource.
         */
        static V8_DEPRECATED("Use maybe version",
                             Local<String> NewExternal(
                                 Isolate* isolate, ExternalStringResource* resource));
        static V8_WARN_UNUSED_RESULT MaybeLocal<String> NewExternalTwoByte(
            Isolate* isolate, ExternalStringResource* resource);

        /**
         * Associate an external string resource with this string by transforming it
         * in place so that existing references to this string in the JavaScript heap
         * will use the external string resource. The external string resource's
         * character contents need to be equivalent to this string.
         * Returns true if the string has been changed to be an external string.
         * The string is not modified if the operation fails. See NewExternal for
         * information on the lifetime of the resource.
         */
        bool MakeExternal(ExternalStringResource* resource);

        /**
         * Creates a new external string using the one-byte data defined in the given
         * resource. When the external string is no longer live on V8's heap the
         * resource will be disposed by calling its Dispose method. The caller of
         * this function should not otherwise delete or modify the resource. Neither
         * should the underlying buffer be deallocated or modified except through the
         * destructor of the external string resource.
         */
        static V8_DEPRECATE_SOON(
            "Use maybe version",
            Local<String> NewExternal(Isolate* isolate,
                                      ExternalOneByteStringResource* resource));
        static V8_WARN_UNUSED_RESULT MaybeLocal<String> NewExternalOneByte(
            Isolate* isolate, ExternalOneByteStringResource* resource);

        /**
         * Associate an external string resource with this string by transforming it
         * in place so that existing references to this string in the JavaScript heap
         * will use the external string resource. The external string resource's
         * character contents need to be equivalent to this string.
         * Returns true if the string has been changed to be an external string.
         * The string is not modified if the operation fails. See NewExternal for
         * information on the lifetime of the resource.
         */
        bool MakeExternal(ExternalOneByteStringResource* resource);

        /**
         * Returns true if this string can be made external.
         */
        bool CanMakeExternal();

        /**
         * Converts an object to a UTF-8-encoded character array.  Useful if
         * you want to print the object.  If conversion to a string fails
         * (e.g. due to an exception in the toString() method of the object)
         * then the length() method returns 0 and the * operator returns
         * NULL.
         */
        class V8_EXPORT Utf8Value {
            public:
                explicit Utf8Value(Local<v8::Value> obj);
                ~Utf8Value();
                char* operator*() {
                    return str_;
                }
                const char* operator*() const {
                    return str_;
                }
                int length() const {
                    return length_;
                }

                // Disallow copying and assigning.
                Utf8Value(const Utf8Value&) = delete;
                void operator=(const Utf8Value&) = delete;

            private:
                char* str_;
                int length_;
        };

        /**
         * Converts an object to a two-byte string.
         * If conversion to a string fails (eg. due to an exception in the toString()
         * method of the object) then the length() method returns 0 and the * operator
         * returns NULL.
         */
        class V8_EXPORT Value {
            public:
                explicit Value(Local<v8::Value> obj);
                ~Value();
                uint16_t* operator*() {
                    return str_;
                }
                const uint16_t* operator*() const {
                    return str_;
                }
                int length() const {
                    return length_;
                }

                // Disallow copying and assigning.
                Value(const Value&) = delete;
                void operator=(const Value&) = delete;

            private:
                uint16_t* str_;
                int length_;
        };

    private:
        void VerifyExternalStringResourceBase(ExternalStringResourceBase* v,
                                              Encoding encoding) const;
        void VerifyExternalStringResource(ExternalStringResource* val) const;
        static void CheckCast(v8::Value* obj);
};


/**
 * A JavaScript symbol (ECMA-262 edition 6)
 *
 * This is an experimental feature. Use at your own risk.
 */
class V8_EXPORT Symbol : public Name {
    public:
        // Returns the print name string of the symbol, or undefined if none.
        Local<Value> Name() const;

        // Create a symbol. If name is not empty, it will be used as the description.
        static Local<Symbol> New(Isolate* isolate,
                                 Local<String> name = Local<String>());

        // Access global symbol registry.
        // Note that symbols created this way are never collected, so
        // they should only be used for statically fixed properties.
        // Also, there is only one global name space for the names used as keys.
        // To minimize the potential for clashes, use qualified names as keys.
        static Local<Symbol> For(Isolate* isolate, Local<String> name);

        // Retrieve a global symbol. Similar to |For|, but using a separate
        // registry that is not accessible by (and cannot clash with) JavaScript code.
        static Local<Symbol> ForApi(Isolate* isolate, Local<String> name);

        // Well-known symbols
        static Local<Symbol> GetIterator(Isolate* isolate);
        static Local<Symbol> GetUnscopables(Isolate* isolate);
        static Local<Symbol> GetToStringTag(Isolate* isolate);
        static Local<Symbol> GetIsConcatSpreadable(Isolate* isolate);

        V8_INLINE static Symbol* Cast(v8::Value* obj);

    private:
        Symbol();
        static void CheckCast(v8::Value* obj);
};


/**
 * A private symbol
 *
 * This is an experimental feature. Use at your own risk.
 */
class V8_EXPORT Private : public Data {
    public:
        // Returns the print name string of the private symbol, or undefined if none.
        Local<Value> Name() const;

        // Create a private symbol. If name is not empty, it will be the description.
        static Local<Private> New(Isolate* isolate,
                                  Local<String> name = Local<String>());

        // Retrieve a global private symbol. If a symbol with this name has not
        // been retrieved in the same isolate before, it is created.
        // Note that private symbols created this way are never collected, so
        // they should only be used for statically fixed properties.
        // Also, there is only one global name space for the names used as keys.
        // To minimize the potential for clashes, use qualified names as keys,
        // e.g., "Class#property".
        static Local<Private> ForApi(Isolate* isolate, Local<String> name);

    private:
        Private();
};


/**
 * A JavaScript number value (ECMA-262, 4.3.20)
 */
class V8_EXPORT Number : public Primitive {
    public:
        double Value() const;
        static Local<Number> New(Isolate* isolate, double value);
        V8_INLINE static Number* Cast(v8::Value* obj);
    private:
        Number();
        static void CheckCast(v8::Value* obj);
};


/**
 * A JavaScript value representing a signed integer.
 */
class V8_EXPORT Integer : public Number {
    public:
        static Local<Integer> New(Isolate* isolate, int32_t value);
        static Local<Integer> NewFromUnsigned(Isolate* isolate, uint32_t value);
        int64_t Value() const;
        V8_INLINE static Integer* Cast(v8::Value* obj);
    private:
        Integer();
        static void CheckCast(v8::Value* obj);
};


/**
 * A JavaScript value representing a 32-bit signed integer.
 */
class V8_EXPORT Int32 : public Integer {
    public:
        int32_t Value() const;
        V8_INLINE static Int32* Cast(v8::Value* obj);

    private:
        Int32();
        static void CheckCast(v8::Value* obj);
};


/**
 * A JavaScript value representing a 32-bit unsigned integer.
 */
class V8_EXPORT Uint32 : public Integer {
    public:
        uint32_t Value() const;
        V8_INLINE static Uint32* Cast(v8::Value* obj);

    private:
        Uint32();
        static void CheckCast(v8::Value* obj);
};

/**
 * PropertyAttribute.
 */
enum PropertyAttribute {
    /** None. **/
    None = 0,
    /** ReadOnly, i.e., not writable. **/
    ReadOnly = 1 << 0,
    /** DontEnum, i.e., not enumerable. **/
    DontEnum = 1 << 1,
    /** DontDelete, i.e., not configurable. **/
    DontDelete = 1 << 2
};

/**
 * Accessor[Getter|Setter] are used as callback functions when
 * setting|getting a particular property. See Object and ObjectTemplate's
 * method SetAccessor.
 */
typedef void (*AccessorGetterCallback)(
    Local<String> property,
    const PropertyCallbackInfo<Value>& info);
typedef void (*AccessorNameGetterCallback)(
    Local<Name> property,
    const PropertyCallbackInfo<Value>& info);


typedef void (*AccessorSetterCallback)(
    Local<String> property,
    Local<Value> value,
    const PropertyCallbackInfo<void>& info);
typedef void (*AccessorNameSetterCallback)(
    Local<Name> property,
    Local<Value> value,
    const PropertyCallbackInfo<void>& info);


/**
 * Access control specifications.
 *
 * Some accessors should be accessible across contexts.  These
 * accessors have an explicit access control parameter which specifies
 * the kind of cross-context access that should be allowed.
 *
 * TODO(dcarney): Remove PROHIBITS_OVERWRITING as it is now unused.
 */
enum AccessControl {
    DEFAULT               = 0,
    ALL_CAN_READ          = 1,
    ALL_CAN_WRITE         = 1 << 1,
    PROHIBITS_OVERWRITING = 1 << 2
};

/**
 * Property filter bits. They can be or'ed to build a composite filter.
 */
enum PropertyFilter {
    ALL_PROPERTIES = 0,
    ONLY_WRITABLE = 1,
    ONLY_ENUMERABLE = 2,
    ONLY_CONFIGURABLE = 4,
    SKIP_STRINGS = 8,
    SKIP_SYMBOLS = 16
};

/**
 * Keys/Properties filter enums:
 *
 * KeyCollectionMode limits the range of collected properties. kOwnOnly limits
 * the collected properties to the given Object only. kIncludesPrototypes will
 * include all keys of the objects's prototype chain as well.
 */
enum class KeyCollectionMode { kOwnOnly, kIncludePrototypes };

/**
 * kIncludesIndices allows for integer indices to be collected, while
 * kSkipIndices will exclude integer indicies from being collected.
 */
enum class IndexFilter { kIncludeIndices, kSkipIndices };

/**
 * Integrity level for objects.
 */
enum class IntegrityLevel { kFrozen, kSealed };

/**
 * A JavaScript object (ECMA-262, 4.3.3)
 */
class V8_EXPORT Object : public Value {
    public:
        V8_DEPRECATE_SOON("Use maybe version",
                          bool Set(Local<Value> key, Local<Value> value));
        V8_WARN_UNUSED_RESULT Maybe<bool> Set(Local<Context> context,
                                              Local<Value> key, Local<Value> value);

        V8_DEPRECATE_SOON("Use maybe version",
                          bool Set(uint32_t index, Local<Value> value));
        V8_WARN_UNUSED_RESULT Maybe<bool> Set(Local<Context> context, uint32_t index,
                                              Local<Value> value);

        // Implements CreateDataProperty (ECMA-262, 7.3.4).
        //
        // Defines a configurable, writable, enumerable property with the given value
        // on the object unless the property already exists and is not configurable
        // or the object is not extensible.
        //
        // Returns true on success.
        V8_WARN_UNUSED_RESULT Maybe<bool> CreateDataProperty(Local<Context> context,
                Local<Name> key,
                Local<Value> value);
        V8_WARN_UNUSED_RESULT Maybe<bool> CreateDataProperty(Local<Context> context,
                uint32_t index,
                Local<Value> value);

        // Implements DefineOwnProperty.
        //
        // In general, CreateDataProperty will be faster, however, does not allow
        // for specifying attributes.
        //
        // Returns true on success.
        V8_WARN_UNUSED_RESULT Maybe<bool> DefineOwnProperty(
            Local<Context> context, Local<Name> key, Local<Value> value,
            PropertyAttribute attributes = None);

        // Implements Object.DefineProperty(O, P, Attributes), see Ecma-262 19.1.2.4.
        //
        // The defineProperty function is used to add an own property or
        // update the attributes of an existing own property of an object.
        //
        // Both data and accessor descriptors can be used.
        //
        // In general, CreateDataProperty is faster, however, does not allow
        // for specifying attributes or an accessor descriptor.
        //
        // The PropertyDescriptor can change when redefining a property.
        //
        // Returns true on success.
        V8_WARN_UNUSED_RESULT Maybe<bool> DefineProperty(
            Local<Context> context, Local<Name> key, PropertyDescriptor& descriptor);

        // Sets an own property on this object bypassing interceptors and
        // overriding accessors or read-only properties.
        //
        // Note that if the object has an interceptor the property will be set
        // locally, but since the interceptor takes precedence the local property
        // will only be returned if the interceptor doesn't return a value.
        //
        // Note also that this only works for named properties.
        V8_DEPRECATED("Use CreateDataProperty / DefineOwnProperty",
                      bool ForceSet(Local<Value> key, Local<Value> value,
                                    PropertyAttribute attribs = None));
        V8_DEPRECATE_SOON("Use CreateDataProperty / DefineOwnProperty",
                          Maybe<bool> ForceSet(Local<Context> context,
                                               Local<Value> key, Local<Value> value,
                                               PropertyAttribute attribs = None));

        V8_DEPRECATE_SOON("Use maybe version", Local<Value> Get(Local<Value> key));
        V8_WARN_UNUSED_RESULT MaybeLocal<Value> Get(Local<Context> context,
                Local<Value> key);

        V8_DEPRECATE_SOON("Use maybe version", Local<Value> Get(uint32_t index));
        V8_WARN_UNUSED_RESULT MaybeLocal<Value> Get(Local<Context> context,
                uint32_t index);

        /**
         * Gets the property attributes of a property which can be None or
         * any combination of ReadOnly, DontEnum and DontDelete. Returns
         * None when the property doesn't exist.
         */
        V8_DEPRECATED("Use maybe version",
                      PropertyAttribute GetPropertyAttributes(Local<Value> key));
        V8_WARN_UNUSED_RESULT Maybe<PropertyAttribute> GetPropertyAttributes(
            Local<Context> context, Local<Value> key);

        /**
         * Returns Object.getOwnPropertyDescriptor as per ES5 section 15.2.3.3.
         */
        V8_DEPRECATED("Use maybe version",
                      Local<Value> GetOwnPropertyDescriptor(Local<String> key));
        V8_WARN_UNUSED_RESULT MaybeLocal<Value> GetOwnPropertyDescriptor(
            Local<Context> context, Local<String> key);

        V8_DEPRECATE_SOON("Use maybe version", bool Has(Local<Value> key));
        /**
         * Object::Has() calls the abstract operation HasProperty(O, P) described
         * in ECMA-262, 7.3.10. Has() returns
         * true, if the object has the property, either own or on the prototype chain.
         * Interceptors, i.e., PropertyQueryCallbacks, are called if present.
         *
         * Has() has the same side effects as JavaScript's `variable in object`.
         * For example, calling Has() on a revoked proxy will throw an exception.
         *
         * \note Has() converts the key to a name, which possibly calls back into
         * JavaScript.
         *
         * See also v8::Object::HasOwnProperty() and
         * v8::Object::HasRealNamedProperty().
         */
        V8_WARN_UNUSED_RESULT Maybe<bool> Has(Local<Context> context,
                                              Local<Value> key);

        V8_DEPRECATE_SOON("Use maybe version", bool Delete(Local<Value> key));
        // TODO(dcarney): mark V8_WARN_UNUSED_RESULT
        Maybe<bool> Delete(Local<Context> context, Local<Value> key);

        V8_DEPRECATED("Use maybe version", bool Has(uint32_t index));
        V8_WARN_UNUSED_RESULT Maybe<bool> Has(Local<Context> context, uint32_t index);

        V8_DEPRECATED("Use maybe version", bool Delete(uint32_t index));
        // TODO(dcarney): mark V8_WARN_UNUSED_RESULT
        Maybe<bool> Delete(Local<Context> context, uint32_t index);

        V8_DEPRECATED("Use maybe version",
                      bool SetAccessor(Local<String> name,
                                       AccessorGetterCallback getter,
                                       AccessorSetterCallback setter = 0,
                                       Local<Value> data = Local<Value>(),
                                       AccessControl settings = DEFAULT,
                                       PropertyAttribute attribute = None));
        V8_DEPRECATED("Use maybe version",
                      bool SetAccessor(Local<Name> name,
                                       AccessorNameGetterCallback getter,
                                       AccessorNameSetterCallback setter = 0,
                                       Local<Value> data = Local<Value>(),
                                       AccessControl settings = DEFAULT,
                                       PropertyAttribute attribute = None));
        // TODO(dcarney): mark V8_WARN_UNUSED_RESULT
        Maybe<bool> SetAccessor(Local<Context> context, Local<Name> name,
                                AccessorNameGetterCallback getter,
                                AccessorNameSetterCallback setter = 0,
                                MaybeLocal<Value> data = MaybeLocal<Value>(),
                                AccessControl settings = DEFAULT,
                                PropertyAttribute attribute = None);

        void SetAccessorProperty(Local<Name> name, Local<Function> getter,
                                 Local<Function> setter = Local<Function>(),
                                 PropertyAttribute attribute = None,
                                 AccessControl settings = DEFAULT);

        /**
         * Functionality for private properties.
         * This is an experimental feature, use at your own risk.
         * Note: Private properties are not inherited. Do not rely on this, since it
         * may change.
         */
        Maybe<bool> HasPrivate(Local<Context> context, Local<Private> key);
        Maybe<bool> SetPrivate(Local<Context> context, Local<Private> key,
                               Local<Value> value);
        Maybe<bool> DeletePrivate(Local<Context> context, Local<Private> key);
        MaybeLocal<Value> GetPrivate(Local<Context> context, Local<Private> key);

        /**
         * Returns an array containing the names of the enumerable properties
         * of this object, including properties from prototype objects.  The
         * array returned by this method contains the same values as would
         * be enumerated by a for-in statement over this object.
         */
        V8_DEPRECATE_SOON("Use maybe version", Local<Array> GetPropertyNames());
        V8_WARN_UNUSED_RESULT MaybeLocal<Array> GetPropertyNames(
            Local<Context> context);
        V8_WARN_UNUSED_RESULT MaybeLocal<Array> GetPropertyNames(
            Local<Context> context, KeyCollectionMode mode,
            PropertyFilter property_filter, IndexFilter index_filter);

        /**
         * This function has the same functionality as GetPropertyNames but
         * the returned array doesn't contain the names of properties from
         * prototype objects.
         */
        V8_DEPRECATE_SOON("Use maybe version", Local<Array> GetOwnPropertyNames());
        V8_WARN_UNUSED_RESULT MaybeLocal<Array> GetOwnPropertyNames(
            Local<Context> context);

        /**
         * Returns an array containing the names of the filtered properties
         * of this object, including properties from prototype objects.  The
         * array returned by this method contains the same values as would
         * be enumerated by a for-in statement over this object.
         */
        V8_WARN_UNUSED_RESULT MaybeLocal<Array> GetOwnPropertyNames(
            Local<Context> context, PropertyFilter filter);

        /**
         * Get the prototype object.  This does not skip objects marked to
         * be skipped by __proto__ and it does not consult the security
         * handler.
         */
        Local<Value> GetPrototype();

        /**
         * Set the prototype object.  This does not skip objects marked to
         * be skipped by __proto__ and it does not consult the security
         * handler.
         */
        V8_DEPRECATED("Use maybe version", bool SetPrototype(Local<Value> prototype));
        V8_WARN_UNUSED_RESULT Maybe<bool> SetPrototype(Local<Context> context,
                Local<Value> prototype);

        /**
         * Finds an instance of the given function template in the prototype
         * chain.
         */
        Local<Object> FindInstanceInPrototypeChain(Local<FunctionTemplate> tmpl);

        /**
         * Call builtin Object.prototype.toString on this object.
         * This is different from Value::ToString() that may call
         * user-defined toString function. This one does not.
         */
        V8_DEPRECATED("Use maybe version", Local<String> ObjectProtoToString());
        V8_WARN_UNUSED_RESULT MaybeLocal<String> ObjectProtoToString(
            Local<Context> context);

        /**
         * Returns the name of the function invoked as a constructor for this object.
         */
        Local<String> GetConstructorName();

        /**
         * Sets the integrity level of the object.
         */
        Maybe<bool> SetIntegrityLevel(Local<Context> context, IntegrityLevel level);

        /** Gets the number of internal fields for this Object. */
        int InternalFieldCount();

        /** Same as above, but works for Persistents */
        V8_INLINE static int InternalFieldCount(
            const PersistentBase<Object>& object) {
            return object.val_->InternalFieldCount();
        }

        /** Gets the value from an internal field. */
        V8_INLINE Local<Value> GetInternalField(int index);

        /** Sets the value in an internal field. */
        void SetInternalField(int index, Local<Value> value);

        /**
         * Gets a 2-byte-aligned native pointer from an internal field. This field
         * must have been set by SetAlignedPointerInInternalField, everything else
         * leads to undefined behavior.
         */
        V8_INLINE void* GetAlignedPointerFromInternalField(int index);

        /** Same as above, but works for Persistents */
        V8_INLINE static void* GetAlignedPointerFromInternalField(
            const PersistentBase<Object>& object, int index) {
            return object.val_->GetAlignedPointerFromInternalField(index);
        }

        /**
         * Sets a 2-byte-aligned native pointer in an internal field. To retrieve such
         * a field, GetAlignedPointerFromInternalField must be used, everything else
         * leads to undefined behavior.
         */
        void SetAlignedPointerInInternalField(int index, void* value);
        void SetAlignedPointerInInternalFields(int argc, int indices[],
                                               void* values[]);

        // Testers for local properties.
        V8_DEPRECATED("Use maybe version", bool HasOwnProperty(Local<String> key));

        /**
         * HasOwnProperty() is like JavaScript's Object.prototype.hasOwnProperty().
         *
         * See also v8::Object::Has() and v8::Object::HasRealNamedProperty().
         */
        V8_WARN_UNUSED_RESULT Maybe<bool> HasOwnProperty(Local<Context> context,
                Local<Name> key);
        V8_WARN_UNUSED_RESULT Maybe<bool> HasOwnProperty(Local<Context> context,
                uint32_t index);
        V8_DEPRECATE_SOON("Use maybe version",
                          bool HasRealNamedProperty(Local<String> key));
        /**
         * Use HasRealNamedProperty() if you want to check if an object has an own
         * property without causing side effects, i.e., without calling interceptors.
         *
         * This function is similar to v8::Object::HasOwnProperty(), but it does not
         * call interceptors.
         *
         * \note Consider using non-masking interceptors, i.e., the interceptors are
         * not called if the receiver has the real named property. See
         * `v8::PropertyHandlerFlags::kNonMasking`.
         *
         * See also v8::Object::Has().
         */
        V8_WARN_UNUSED_RESULT Maybe<bool> HasRealNamedProperty(Local<Context> context,
                Local<Name> key);
        V8_DEPRECATE_SOON("Use maybe version",
                          bool HasRealIndexedProperty(uint32_t index));
        V8_WARN_UNUSED_RESULT Maybe<bool> HasRealIndexedProperty(
            Local<Context> context, uint32_t index);
        V8_DEPRECATE_SOON("Use maybe version",
                          bool HasRealNamedCallbackProperty(Local<String> key));
        V8_WARN_UNUSED_RESULT Maybe<bool> HasRealNamedCallbackProperty(
            Local<Context> context, Local<Name> key);

        /**
         * If result.IsEmpty() no real property was located in the prototype chain.
         * This means interceptors in the prototype chain are not called.
         */
        V8_DEPRECATED(
            "Use maybe version",
            Local<Value> GetRealNamedPropertyInPrototypeChain(Local<String> key));
        V8_WARN_UNUSED_RESULT MaybeLocal<Value> GetRealNamedPropertyInPrototypeChain(
            Local<Context> context, Local<Name> key);

        /**
         * Gets the property attributes of a real property in the prototype chain,
         * which can be None or any combination of ReadOnly, DontEnum and DontDelete.
         * Interceptors in the prototype chain are not called.
         */
        V8_DEPRECATED(
            "Use maybe version",
            Maybe<PropertyAttribute> GetRealNamedPropertyAttributesInPrototypeChain(
                Local<String> key));
        V8_WARN_UNUSED_RESULT Maybe<PropertyAttribute>
        GetRealNamedPropertyAttributesInPrototypeChain(Local<Context> context,
                Local<Name> key);

        /**
         * If result.IsEmpty() no real property was located on the object or
         * in the prototype chain.
         * This means interceptors in the prototype chain are not called.
         */
        V8_DEPRECATED("Use maybe version",
                      Local<Value> GetRealNamedProperty(Local<String> key));
        V8_WARN_UNUSED_RESULT MaybeLocal<Value> GetRealNamedProperty(
            Local<Context> context, Local<Name> key);

        /**
         * Gets the property attributes of a real property which can be
         * None or any combination of ReadOnly, DontEnum and DontDelete.
         * Interceptors in the prototype chain are not called.
         */
        V8_DEPRECATED("Use maybe version",
                      Maybe<PropertyAttribute> GetRealNamedPropertyAttributes(
                          Local<String> key));
        V8_WARN_UNUSED_RESULT Maybe<PropertyAttribute> GetRealNamedPropertyAttributes(
            Local<Context> context, Local<Name> key);

        /** Tests for a named lookup interceptor.*/
        bool HasNamedLookupInterceptor();

        /** Tests for an index lookup interceptor.*/
        bool HasIndexedLookupInterceptor();

        /**
         * Returns the identity hash for this object. The current implementation
         * uses a hidden property on the object to store the identity hash.
         *
         * The return value will never be 0. Also, it is not guaranteed to be
         * unique.
         */
        int GetIdentityHash();

        /**
         * Clone this object with a fast but shallow copy.  Values will point
         * to the same values as the original object.
         */
        // TODO(dcarney): take an isolate and optionally bail out?
        Local<Object> Clone();

        /**
         * Returns the context in which the object was created.
         */
        Local<Context> CreationContext();

        /** Same as above, but works for Persistents */
        V8_INLINE static Local<Context> CreationContext(
            const PersistentBase<Object>& object) {
            return object.val_->CreationContext();
        }

        /**
         * Checks whether a callback is set by the
         * ObjectTemplate::SetCallAsFunctionHandler method.
         * When an Object is callable this method returns true.
         */
        bool IsCallable();

        /**
         * True if this object is a constructor.
         */
        bool IsConstructor();

        /**
         * Call an Object as a function if a callback is set by the
         * ObjectTemplate::SetCallAsFunctionHandler method.
         */
        V8_DEPRECATED("Use maybe version",
                      Local<Value> CallAsFunction(Local<Value> recv, int argc,
                              Local<Value> argv[]));
        V8_WARN_UNUSED_RESULT MaybeLocal<Value> CallAsFunction(Local<Context> context,
                Local<Value> recv,
                int argc,
                Local<Value> argv[]);

        /**
         * Call an Object as a constructor if a callback is set by the
         * ObjectTemplate::SetCallAsFunctionHandler method.
         * Note: This method behaves like the Function::NewInstance method.
         */
        V8_DEPRECATED("Use maybe version",
                      Local<Value> CallAsConstructor(int argc, Local<Value> argv[]));
        V8_WARN_UNUSED_RESULT MaybeLocal<Value> CallAsConstructor(
            Local<Context> context, int argc, Local<Value> argv[]);

        /**
         * Return the isolate to which the Object belongs to.
         */
        V8_DEPRECATE_SOON("Keep track of isolate correctly", Isolate* GetIsolate());

        static Local<Object> New(Isolate* isolate);

        V8_INLINE static Object* Cast(Value* obj);

    private:
        Object();
        static void CheckCast(Value* obj);
        Local<Value> SlowGetInternalField(int index);
        void* SlowGetAlignedPointerFromInternalField(int index);
};


/**
 * An instance of the built-in array constructor (ECMA-262, 15.4.2).
 */
class V8_EXPORT Array : public Object {
    public:
        uint32_t Length() const;

        /**
         * Clones an element at index |index|.  Returns an empty
         * handle if cloning fails (for any reason).
         */
        V8_DEPRECATED("Cloning is not supported.",
                      Local<Object> CloneElementAt(uint32_t index));
        V8_DEPRECATED("Cloning is not supported.",
                      MaybeLocal<Object> CloneElementAt(Local<Context> context,
                              uint32_t index));

        /**
         * Creates a JavaScript array with the given length. If the length
         * is negative the returned array will have length 0.
         */
        static Local<Array> New(Isolate* isolate, int length = 0);

        V8_INLINE static Array* Cast(Value* obj);
    private:
        Array();
        static void CheckCast(Value* obj);
};


/**
 * An instance of the built-in Map constructor (ECMA-262, 6th Edition, 23.1.1).
 */
class V8_EXPORT Map : public Object {
    public:
        size_t Size() const;
        void Clear();
        V8_WARN_UNUSED_RESULT MaybeLocal<Value> Get(Local<Context> context,
                Local<Value> key);
        V8_WARN_UNUSED_RESULT MaybeLocal<Map> Set(Local<Context> context,
                Local<Value> key,
                Local<Value> value);
        V8_WARN_UNUSED_RESULT Maybe<bool> Has(Local<Context> context,
                                              Local<Value> key);
        V8_WARN_UNUSED_RESULT Maybe<bool> Delete(Local<Context> context,
                Local<Value> key);

        /**
         * Returns an array of length Size() * 2, where index N is the Nth key and
         * index N + 1 is the Nth value.
         */
        Local<Array> AsArray() const;

        /**
         * Creates a new empty Map.
         */
        static Local<Map> New(Isolate* isolate);

        V8_INLINE static Map* Cast(Value* obj);

    private:
        Map();
        static void CheckCast(Value* obj);
};


/**
 * An instance of the built-in Set constructor (ECMA-262, 6th Edition, 23.2.1).
 */
class V8_EXPORT Set : public Object {
    public:
        size_t Size() const;
        void Clear();
        V8_WARN_UNUSED_RESULT MaybeLocal<Set> Add(Local<Context> context,
                Local<Value> key);
        V8_WARN_UNUSED_RESULT Maybe<bool> Has(Local<Context> context,
                                              Local<Value> key);
        V8_WARN_UNUSED_RESULT Maybe<bool> Delete(Local<Context> context,
                Local<Value> key);

        /**
         * Returns an array of the keys in this Set.
         */
        Local<Array> AsArray() const;

        /**
         * Creates a new empty Set.
         */
        static Local<Set> New(Isolate* isolate);

        V8_INLINE static Set* Cast(Value* obj);

    private:
        Set();
        static void CheckCast(Value* obj);
};


template<typename T>
class ReturnValue {
    public:
        template <class S> V8_INLINE ReturnValue(const ReturnValue<S>& that)
            : value_(that.value_) {
            TYPE_CHECK(T, S);
        }
        // Local setters
        template <typename S>
        V8_INLINE V8_DEPRECATE_SOON("Use Global<> instead",
                                    void Set(const Persistent<S>& handle));
        template <typename S>
        V8_INLINE void Set(const Global<S>& handle);
        template <typename S>
        V8_INLINE void Set(const Local<S> handle);
        // Fast primitive setters
        V8_INLINE void Set(bool value);
        V8_INLINE void Set(double i);
        V8_INLINE void Set(int32_t i);
        V8_INLINE void Set(uint32_t i);
        // Fast JS primitive setters
        V8_INLINE void SetNull();
        V8_INLINE void SetUndefined();
        V8_INLINE void SetEmptyString();
        // Convenience getter for Isolate
        V8_INLINE Isolate* GetIsolate() const;

        // Pointer setter: Uncompilable to prevent inadvertent misuse.
        template <typename S>
        V8_INLINE void Set(S* whatever);

        // Getter. Creates a new Local<> so it comes with a certain performance
        // hit. If the ReturnValue was not yet set, this will return the undefined
        // value.
        V8_INLINE Local<Value> Get() const;

    private:
        template<class F> friend class ReturnValue;
        template<class F> friend class FunctionCallbackInfo;
        template<class F> friend class PropertyCallbackInfo;
        template <class F, class G, class H>
        friend class PersistentValueMapBase;
        V8_INLINE void SetInternal(internal::Object* value) {
            *value_ = value;
        }
        V8_INLINE internal::Object* GetDefaultValue();
        V8_INLINE explicit ReturnValue(internal::Object** slot);
        internal::Object** value_;
};


/**
 * The argument information given to function call callbacks.  This
 * class provides access to information about the context of the call,
 * including the receiver, the number and values of arguments, and
 * the holder of the function.
 */
template<typename T>
class FunctionCallbackInfo {
    public:
        V8_INLINE int Length() const;
        V8_INLINE Local<Value> operator[](int i) const;
        V8_INLINE V8_DEPRECATED("Use Data() to explicitly pass Callee instead",
                                Local<Function> Callee() const);
        V8_INLINE Local<Object> This() const;
        V8_INLINE Local<Object> Holder() const;
        V8_INLINE Local<Value> NewTarget() const;
        V8_INLINE bool IsConstructCall() const;
        V8_INLINE Local<Value> Data() const;
        V8_INLINE Isolate* GetIsolate() const;
        V8_INLINE ReturnValue<T> GetReturnValue() const;
        // This shouldn't be public, but the arm compiler needs it.
        static const int kArgsLength = 8;

    protected:
        friend class internal::FunctionCallbackArguments;
        friend class internal::CustomArguments<FunctionCallbackInfo>;
        static const int kHolderIndex = 0;
        static const int kIsolateIndex = 1;
        static const int kReturnValueDefaultValueIndex = 2;
        static const int kReturnValueIndex = 3;
        static const int kDataIndex = 4;
        static const int kCalleeIndex = 5;
        static const int kContextSaveIndex = 6;
        static const int kNewTargetIndex = 7;

        V8_INLINE FunctionCallbackInfo(internal::Object** implicit_args,
                                       internal::Object** values, int length);
        internal::Object** implicit_args_;
        internal::Object** values_;
        int length_;
};


/**
 * The information passed to a property callback about the context
 * of the property access.
 */
template<typename T>
class PropertyCallbackInfo {
    public:
        /**
         * \return The isolate of the property access.
         */
        V8_INLINE Isolate* GetIsolate() const;

        /**
         * \return The data set in the configuration, i.e., in
         * `NamedPropertyHandlerConfiguration` or
         * `IndexedPropertyHandlerConfiguration.`
         */
        V8_INLINE Local<Value> Data() const;

        /**
         * \return The receiver. In many cases, this is the object on which the
         * property access was intercepted. When using
         * `Reflect.Get`, `Function.prototype.call`, or similar functions, it is the
         * object passed in as receiver or thisArg.
         *
         * \code
         *  void GetterCallback(Local<Name> name,
         *                      const v8::PropertyCallbackInfo<v8::Value>& info) {
         *     auto context = info.GetIsolate()->GetCurrentContext();
         *
         *     v8::Local<v8::Value> a_this =
         *         info.This()
         *             ->GetRealNamedProperty(context, v8_str("a"))
         *             .ToLocalChecked();
         *     v8::Local<v8::Value> a_holder =
         *         info.Holder()
         *             ->GetRealNamedProperty(context, v8_str("a"))
         *             .ToLocalChecked();
         *
         *    CHECK(v8_str("r")->Equals(context, a_this).FromJust());
         *    CHECK(v8_str("obj")->Equals(context, a_holder).FromJust());
         *
         *    info.GetReturnValue().Set(name);
         *  }
         *
         *  v8::Local<v8::FunctionTemplate> templ =
         *  v8::FunctionTemplate::New(isolate);
         *  templ->InstanceTemplate()->SetHandler(
         *      v8::NamedPropertyHandlerConfiguration(GetterCallback));
         *  LocalContext env;
         *  env->Global()
         *      ->Set(env.local(), v8_str("obj"), templ->GetFunction(env.local())
         *                                           .ToLocalChecked()
         *                                           ->NewInstance(env.local())
         *                                           .ToLocalChecked())
         *      .FromJust();
         *
         *  CompileRun("obj.a = 'obj'; var r = {a: 'r'}; Reflect.get(obj, 'x', r)");
         * \endcode
         */
        V8_INLINE Local<Object> This() const;

        /**
         * \return The object in the prototype chain of the receiver that has the
         * interceptor. Suppose you have `x` and its prototype is `y`, and `y`
         * has an interceptor. Then `info.This()` is `x` and `info.Holder()` is `y`.
         * The Holder() could be a hidden object (the global object, rather
         * than the global proxy).
         *
         * \note For security reasons, do not pass the object back into the runtime.
         */
        V8_INLINE Local<Object> Holder() const;

        /**
         * \return The return value of the callback.
         * Can be changed by calling Set().
         * \code
         * info.GetReturnValue().Set(...)
         * \endcode
         *
         */
        V8_INLINE ReturnValue<T> GetReturnValue() const;

        /**
         * \return True if the intercepted function should throw if an error occurs.
         * Usually, `true` corresponds to `'use strict'`.
         *
         * \note Always `false` when intercepting `Reflect.Set()`
         * independent of the language mode.
         */
        V8_INLINE bool ShouldThrowOnError() const;

        // This shouldn't be public, but the arm compiler needs it.
        static const int kArgsLength = 7;

    protected:
        friend class MacroAssembler;
        friend class internal::PropertyCallbackArguments;
        friend class internal::CustomArguments<PropertyCallbackInfo>;
        static const int kShouldThrowOnErrorIndex = 0;
        static const int kHolderIndex = 1;
        static const int kIsolateIndex = 2;
        static const int kReturnValueDefaultValueIndex = 3;
        static const int kReturnValueIndex = 4;
        static const int kDataIndex = 5;
        static const int kThisIndex = 6;

        V8_INLINE PropertyCallbackInfo(internal::Object** args) : args_(args) {}
        internal::Object** args_;
};


typedef void (*FunctionCallback)(const FunctionCallbackInfo<Value>& info);

enum class ConstructorBehavior { kThrow, kAllow };

/**
 * A JavaScript function object (ECMA-262, 15.3).
 */
class V8_EXPORT Function : public Object {
    public:
        /**
         * Create a function in the current execution context
         * for a given FunctionCallback.
         */
        static MaybeLocal<Function> New(
            Local<Context> context, FunctionCallback callback,
            Local<Value> data = Local<Value>(), int length = 0,
            ConstructorBehavior behavior = ConstructorBehavior::kAllow);
        static V8_DEPRECATE_SOON(
            "Use maybe version",
            Local<Function> New(Isolate* isolate, FunctionCallback callback,
                                Local<Value> data = Local<Value>(), int length = 0));

        V8_DEPRECATED("Use maybe version",
                      Local<Object> NewInstance(int argc, Local<Value> argv[]) const);
        V8_WARN_UNUSED_RESULT MaybeLocal<Object> NewInstance(
            Local<Context> context, int argc, Local<Value> argv[]) const;

        V8_DEPRECATED("Use maybe version", Local<Object> NewInstance() const);
        V8_WARN_UNUSED_RESULT MaybeLocal<Object> NewInstance(
            Local<Context> context) const {
            return NewInstance(context, 0, nullptr);
        }

        V8_DEPRECATE_SOON("Use maybe version",
                          Local<Value> Call(Local<Value> recv, int argc,
                                            Local<Value> argv[]));
        V8_WARN_UNUSED_RESULT MaybeLocal<Value> Call(Local<Context> context,
                Local<Value> recv, int argc,
                Local<Value> argv[]);

        void SetName(Local<String> name);
        Local<Value> GetName() const;

        /**
         * Name inferred from variable or property assignment of this function.
         * Used to facilitate debugging and profiling of JavaScript code written
         * in an OO style, where many functions are anonymous but are assigned
         * to object properties.
         */
        Local<Value> GetInferredName() const;

        /**
         * displayName if it is set, otherwise name if it is configured, otherwise
         * function name, otherwise inferred name.
         */
        Local<Value> GetDebugName() const;

        /**
         * User-defined name assigned to the "displayName" property of this function.
         * Used to facilitate debugging and profiling of JavaScript code.
         */
        Local<Value> GetDisplayName() const;

        /**
         * Returns zero based line number of function body and
         * kLineOffsetNotFound if no information available.
         */
        int GetScriptLineNumber() const;
        /**
         * Returns zero based column number of function body and
         * kLineOffsetNotFound if no information available.
         */
        int GetScriptColumnNumber() const;

        /**
         * Tells whether this function is builtin.
         */
        bool IsBuiltin() const;

        /**
         * Returns scriptId.
         */
        int ScriptId() const;

        /**
         * Returns the original function if this function is bound, else returns
         * v8::Undefined.
         */
        Local<Value> GetBoundFunction() const;

        ScriptOrigin GetScriptOrigin() const;
        V8_INLINE static Function* Cast(Value* obj);
        static const int kLineOffsetNotFound;

    private:
        Function();
        static void CheckCast(Value* obj);
};


/**
 * An instance of the built-in Promise constructor (ES6 draft).
 * This API is experimental. Only works with --harmony flag.
 */
class V8_EXPORT Promise : public Object {
    public:
        class V8_EXPORT Resolver : public Object {
            public:
                /**
                 * Create a new resolver, along with an associated promise in pending state.
                 */
                static V8_DEPRECATE_SOON("Use maybe version",
                                         Local<Resolver> New(Isolate* isolate));
                static V8_WARN_UNUSED_RESULT MaybeLocal<Resolver> New(
                    Local<Context> context);

                /**
                 * Extract the associated promise.
                 */
                Local<Promise> GetPromise();

                /**
                 * Resolve/reject the associated promise with a given value.
                 * Ignored if the promise is no longer pending.
                 */
                V8_DEPRECATE_SOON("Use maybe version", void Resolve(Local<Value> value));
                // TODO(dcarney): mark V8_WARN_UNUSED_RESULT
                Maybe<bool> Resolve(Local<Context> context, Local<Value> value);

                V8_DEPRECATE_SOON("Use maybe version", void Reject(Local<Value> value));
                // TODO(dcarney): mark V8_WARN_UNUSED_RESULT
                Maybe<bool> Reject(Local<Context> context, Local<Value> value);

                V8_INLINE static Resolver* Cast(Value* obj);

            private:
                Resolver();
                static void CheckCast(Value* obj);
        };

        /**
         * Register a resolution/rejection handler with a promise.
         * The handler is given the respective resolution/rejection value as
         * an argument. If the promise is already resolved/rejected, the handler is
         * invoked at the end of turn.
         */
        V8_DEPRECATED("Use maybe version",
                      Local<Promise> Catch(Local<Function> handler));
        V8_WARN_UNUSED_RESULT MaybeLocal<Promise> Catch(Local<Context> context,
                Local<Function> handler);

        V8_DEPRECATED("Use maybe version",
                      Local<Promise> Then(Local<Function> handler));
        V8_WARN_UNUSED_RESULT MaybeLocal<Promise> Then(Local<Context> context,
                Local<Function> handler);

        /**
         * Returns true if the promise has at least one derived promise, and
         * therefore resolve/reject handlers (including default handler).
         */
        bool HasHandler();

        V8_INLINE static Promise* Cast(Value* obj);

    private:
        Promise();
        static void CheckCast(Value* obj);
};

/**
 * An instance of a Property Descriptor, see Ecma-262 6.2.4.
 *
 * Properties in a descriptor are present or absent. If you do not set
 * `enumerable`, `configurable`, and `writable`, they are absent. If `value`,
 * `get`, or `set` are absent, but you must specify them in the constructor, use
 * empty handles.
 *
 * Accessors `get` and `set` must be callable or undefined if they are present.
 *
 * \note Only query properties if they are present, i.e., call `x()` only if
 * `has_x()` returns true.
 *
 * \code
 * // var desc = {writable: false}
 * v8::PropertyDescriptor d(Local<Value>()), false);
 * d.value(); // error, value not set
 * if (d.has_writable()) {
 *   d.writable(); // false
 * }
 *
 * // var desc = {value: undefined}
 * v8::PropertyDescriptor d(v8::Undefined(isolate));
 *
 * // var desc = {get: undefined}
 * v8::PropertyDescriptor d(v8::Undefined(isolate), Local<Value>()));
 * \endcode
 */
class V8_EXPORT PropertyDescriptor {
    public:
        // GenericDescriptor
        PropertyDescriptor();

        // DataDescriptor
        PropertyDescriptor(Local<Value> value);

        // DataDescriptor with writable property
        PropertyDescriptor(Local<Value> value, bool writable);

        // AccessorDescriptor
        PropertyDescriptor(Local<Value> get, Local<Value> set);

        ~PropertyDescriptor();

        Local<Value> value() const;
        bool has_value() const;

        Local<Value> get() const;
        bool has_get() const;
        Local<Value> set() const;
        bool has_set() const;

        void set_enumerable(bool enumerable);
        bool enumerable() const;
        bool has_enumerable() const;

        void set_configurable(bool configurable);
        bool configurable() const;
        bool has_configurable() const;

        bool writable() const;
        bool has_writable() const;

        struct PrivateData;
        PrivateData* get_private() const {
            return private_;
        }

        PropertyDescriptor(const PropertyDescriptor&) = delete;
        void operator=(const PropertyDescriptor&) = delete;

    private:
        PrivateData* private_;
};

/**
 * An instance of the built-in Proxy constructor (ECMA-262, 6th Edition,
 * 26.2.1).
 */
class V8_EXPORT Proxy : public Object {
    public:
        Local<Object> GetTarget();
        Local<Value> GetHandler();
        bool IsRevoked();
        void Revoke();

        /**
         * Creates a new Proxy for the target object.
         */
        static MaybeLocal<Proxy> New(Local<Context> context,
                                     Local<Object> local_target,
                                     Local<Object> local_handler);

        V8_INLINE static Proxy* Cast(Value* obj);

    private:
        Proxy();
        static void CheckCast(Value* obj);
};

class V8_EXPORT WasmCompiledModule : public Object {
    public:
        typedef std::pair<std::unique_ptr<const uint8_t[]>, size_t> SerializedModule;

        SerializedModule Serialize();
        static MaybeLocal<WasmCompiledModule> Deserialize(
            Isolate* isolate, const SerializedModule& serialized_data);
        V8_INLINE static WasmCompiledModule* Cast(Value* obj);

    private:
        WasmCompiledModule();
        static void CheckCast(Value* obj);
};

#ifndef V8_ARRAY_BUFFER_INTERNAL_FIELD_COUNT
// The number of required internal fields can be defined by embedder.
#define V8_ARRAY_BUFFER_INTERNAL_FIELD_COUNT 2
#endif


enum class ArrayBufferCreationMode { kInternalized, kExternalized };


/**
 * An instance of the built-in ArrayBuffer constructor (ES6 draft 15.13.5).
 * This API is experimental and may change significantly.
 */
class V8_EXPORT ArrayBuffer : public Object {
    public:
        /**
         * A thread-safe allocator that V8 uses to allocate |ArrayBuffer|'s memory.
         * The allocator is a global V8 setting. It has to be set via
         * Isolate::CreateParams.
         *
         * Memory allocated through this allocator by V8 is accounted for as external
         * memory by V8. Note that V8 keeps track of the memory for all internalized
         * |ArrayBuffer|s. Responsibility for tracking external memory (using
         * Isolate::AdjustAmountOfExternalAllocatedMemory) is handed over to the
         * embedder upon externalization and taken over upon internalization (creating
         * an internalized buffer from an existing buffer).
         *
         * Note that it is unsafe to call back into V8 from any of the allocator
         * functions.
         */
        class V8_EXPORT Allocator { // NOLINT
            public:
                virtual ~Allocator() {}

                /**
                 * Allocate |length| bytes. Return NULL if allocation is not successful.
                 * Memory should be initialized to zeroes.
                 */
                virtual void* Allocate(size_t length) = 0;

                /**
                 * Allocate |length| bytes. Return NULL if allocation is not successful.
                 * Memory does not have to be initialized.
                 */
                virtual void* AllocateUninitialized(size_t length) = 0;

                /**
                 * Free the memory block of size |length|, pointed to by |data|.
                 * That memory is guaranteed to be previously allocated by |Allocate|.
                 */
                virtual void Free(void* data, size_t length) = 0;

                /**
                 * malloc/free based convenience allocator.
                 *
                 * Caller takes ownership.
                 */
                static Allocator* NewDefaultAllocator();
        };

        /**
         * The contents of an |ArrayBuffer|. Externalization of |ArrayBuffer|
         * returns an instance of this class, populated, with a pointer to data
         * and byte length.
         *
         * The Data pointer of ArrayBuffer::Contents is always allocated with
         * Allocator::Allocate that is set via Isolate::CreateParams.
         *
         * This API is experimental and may change significantly.
         */
        class V8_EXPORT Contents { // NOLINT
            public:
                Contents() : data_(NULL), byte_length_(0) {}

                void* Data() const {
                    return data_;
                }
                size_t ByteLength() const {
                    return byte_length_;
                }

            private:
                void* data_;
                size_t byte_length_;

                friend class ArrayBuffer;
        };


        /**
         * Data length in bytes.
         */
        size_t ByteLength() const;

        /**
         * Create a new ArrayBuffer. Allocate |byte_length| bytes.
         * Allocated memory will be owned by a created ArrayBuffer and
         * will be deallocated when it is garbage-collected,
         * unless the object is externalized.
         */
        static Local<ArrayBuffer> New(Isolate* isolate, size_t byte_length);

        /**
         * Create a new ArrayBuffer over an existing memory block.
         * The created array buffer is by default immediately in externalized state.
         * The memory block will not be reclaimed when a created ArrayBuffer
         * is garbage-collected.
         */
        static Local<ArrayBuffer> New(
            Isolate* isolate, void* data, size_t byte_length,
            ArrayBufferCreationMode mode = ArrayBufferCreationMode::kExternalized);

        /**
         * Returns true if ArrayBuffer is externalized, that is, does not
         * own its memory block.
         */
        bool IsExternal() const;

        /**
         * Returns true if this ArrayBuffer may be neutered.
         */
        bool IsNeuterable() const;

        /**
         * Neuters this ArrayBuffer and all its views (typed arrays).
         * Neutering sets the byte length of the buffer and all typed arrays to zero,
         * preventing JavaScript from ever accessing underlying backing store.
         * ArrayBuffer should have been externalized and must be neuterable.
         */
        void Neuter();

        /**
         * Make this ArrayBuffer external. The pointer to underlying memory block
         * and byte length are returned as |Contents| structure. After ArrayBuffer
         * had been externalized, it does no longer own the memory block. The caller
         * should take steps to free memory when it is no longer needed.
         *
         * The memory block is guaranteed to be allocated with |Allocator::Allocate|
         * that has been set via Isolate::CreateParams.
         */
        Contents Externalize();

        /**
         * Get a pointer to the ArrayBuffer's underlying memory block without
         * externalizing it. If the ArrayBuffer is not externalized, this pointer
         * will become invalid as soon as the ArrayBuffer gets garbage collected.
         *
         * The embedder should make sure to hold a strong reference to the
         * ArrayBuffer while accessing this pointer.
         *
         * The memory block is guaranteed to be allocated with |Allocator::Allocate|.
         */
        Contents GetContents();

        V8_INLINE static ArrayBuffer* Cast(Value* obj);

        static const int kInternalFieldCount = V8_ARRAY_BUFFER_INTERNAL_FIELD_COUNT;

    private:
        ArrayBuffer();
        static void CheckCast(Value* obj);
};


#ifndef V8_ARRAY_BUFFER_VIEW_INTERNAL_FIELD_COUNT
// The number of required internal fields can be defined by embedder.
#define V8_ARRAY_BUFFER_VIEW_INTERNAL_FIELD_COUNT 2
#endif


/**
 * A base class for an instance of one of "views" over ArrayBuffer,
 * including TypedArrays and DataView (ES6 draft 15.13).
 *
 * This API is experimental and may change significantly.
 */
class V8_EXPORT ArrayBufferView : public Object {
    public:
        /**
         * Returns underlying ArrayBuffer.
         */
        Local<ArrayBuffer> Buffer();
        /**
         * Byte offset in |Buffer|.
         */
        size_t ByteOffset();
        /**
         * Size of a view in bytes.
         */
        size_t ByteLength();

        /**
         * Copy the contents of the ArrayBufferView's buffer to an embedder defined
         * memory without additional overhead that calling ArrayBufferView::Buffer
         * might incur.
         *
         * Will write at most min(|byte_length|, ByteLength) bytes starting at
         * ByteOffset of the underlying buffer to the memory starting at |dest|.
         * Returns the number of bytes actually written.
         */
        size_t CopyContents(void* dest, size_t byte_length);

        /**
         * Returns true if ArrayBufferView's backing ArrayBuffer has already been
         * allocated.
         */
        bool HasBuffer() const;

        V8_INLINE static ArrayBufferView* Cast(Value* obj);

        static const int kInternalFieldCount =
            V8_ARRAY_BUFFER_VIEW_INTERNAL_FIELD_COUNT;

    private:
        ArrayBufferView();
        static void CheckCast(Value* obj);
};


/**
 * A base class for an instance of TypedArray series of constructors
 * (ES6 draft 15.13.6).
 * This API is experimental and may change significantly.
 */
class V8_EXPORT TypedArray : public ArrayBufferView {
    public:
        /**
         * Number of elements in this typed array
         * (e.g. for Int16Array, |ByteLength|/2).
         */
        size_t Length();

        V8_INLINE static TypedArray* Cast(Value* obj);

    private:
        TypedArray();
        static void CheckCast(Value* obj);
};


/**
 * An instance of Uint8Array constructor (ES6 draft 15.13.6).
 * This API is experimental and may change significantly.
 */
class V8_EXPORT Uint8Array : public TypedArray {
    public:
        static Local<Uint8Array> New(Local<ArrayBuffer> array_buffer,
                                     size_t byte_offset, size_t length);
        static Local<Uint8Array> New(Local<SharedArrayBuffer> shared_array_buffer,
                                     size_t byte_offset, size_t length);
        V8_INLINE static Uint8Array* Cast(Value* obj);

    private:
        Uint8Array();
        static void CheckCast(Value* obj);
};


/**
 * An instance of Uint8ClampedArray constructor (ES6 draft 15.13.6).
 * This API is experimental and may change significantly.
 */
class V8_EXPORT Uint8ClampedArray : public TypedArray {
    public:
        static Local<Uint8ClampedArray> New(Local<ArrayBuffer> array_buffer,
                                            size_t byte_offset, size_t length);
        static Local<Uint8ClampedArray> New(
            Local<SharedArrayBuffer> shared_array_buffer, size_t byte_offset,
            size_t length);
        V8_INLINE static Uint8ClampedArray* Cast(Value* obj);

    private:
        Uint8ClampedArray();
        static void CheckCast(Value* obj);
};

/**
 * An instance of Int8Array constructor (ES6 draft 15.13.6).
 * This API is experimental and may change significantly.
 */
class V8_EXPORT Int8Array : public TypedArray {
    public:
        static Local<Int8Array> New(Local<ArrayBuffer> array_buffer,
                                    size_t byte_offset, size_t length);
        static Local<Int8Array> New(Local<SharedArrayBuffer> shared_array_buffer,
                                    size_t byte_offset, size_t length);
        V8_INLINE static Int8Array* Cast(Value* obj);

    private:
        Int8Array();
        static void CheckCast(Value* obj);
};


/**
 * An instance of Uint16Array constructor (ES6 draft 15.13.6).
 * This API is experimental and may change significantly.
 */
class V8_EXPORT Uint16Array : public TypedArray {
    public:
        static Local<Uint16Array> New(Local<ArrayBuffer> array_buffer,
                                      size_t byte_offset, size_t length);
        static Local<Uint16Array> New(Local<SharedArrayBuffer> shared_array_buffer,
                                      size_t byte_offset, size_t length);
        V8_INLINE static Uint16Array* Cast(Value* obj);

    private:
        Uint16Array();
        static void CheckCast(Value* obj);
};


/**
 * An instance of Int16Array constructor (ES6 draft 15.13.6).
 * This API is experimental and may change significantly.
 */
class V8_EXPORT Int16Array : public TypedArray {
    public:
        static Local<Int16Array> New(Local<ArrayBuffer> array_buffer,
                                     size_t byte_offset, size_t length);
        static Local<Int16Array> New(Local<SharedArrayBuffer> shared_array_buffer,
                                     size_t byte_offset, size_t length);
        V8_INLINE static Int16Array* Cast(Value* obj);

    private:
        Int16Array();
        static void CheckCast(Value* obj);
};


/**
 * An instance of Uint32Array constructor (ES6 draft 15.13.6).
 * This API is experimental and may change significantly.
 */
class V8_EXPORT Uint32Array : public TypedArray {
    public:
        static Local<Uint32Array> New(Local<ArrayBuffer> array_buffer,
                                      size_t byte_offset, size_t length);
        static Local<Uint32Array> New(Local<SharedArrayBuffer> shared_array_buffer,
                                      size_t byte_offset, size_t length);
        V8_INLINE static Uint32Array* Cast(Value* obj);

    private:
        Uint32Array();
        static void CheckCast(Value* obj);
};


/**
 * An instance of Int32Array constructor (ES6 draft 15.13.6).
 * This API is experimental and may change significantly.
 */
class V8_EXPORT Int32Array : public TypedArray {
    public:
        static Local<Int32Array> New(Local<ArrayBuffer> array_buffer,
                                     size_t byte_offset, size_t length);
        static Local<Int32Array> New(Local<SharedArrayBuffer> shared_array_buffer,
                                     size_t byte_offset, size_t length);
        V8_INLINE static Int32Array* Cast(Value* obj);

    private:
        Int32Array();
        static void CheckCast(Value* obj);
};


/**
 * An instance of Float32Array constructor (ES6 draft 15.13.6).
 * This API is experimental and may change significantly.
 */
class V8_EXPORT Float32Array : public TypedArray {
    public:
        static Local<Float32Array> New(Local<ArrayBuffer> array_buffer,
                                       size_t byte_offset, size_t length);
        static Local<Float32Array> New(Local<SharedArrayBuffer> shared_array_buffer,
                                       size_t byte_offset, size_t length);
        V8_INLINE static Float32Array* Cast(Value* obj);

    private:
        Float32Array();
        static void CheckCast(Value* obj);
};


/**
 * An instance of Float64Array constructor (ES6 draft 15.13.6).
 * This API is experimental and may change significantly.
 */
class V8_EXPORT Float64Array : public TypedArray {
    public:
        static Local<Float64Array> New(Local<ArrayBuffer> array_buffer,
                                       size_t byte_offset, size_t length);
        static Local<Float64Array> New(Local<SharedArrayBuffer> shared_array_buffer,
                                       size_t byte_offset, size_t length);
        V8_INLINE static Float64Array* Cast(Value* obj);

    private:
        Float64Array();
        static void CheckCast(Value* obj);
};


/**
 * An instance of DataView constructor (ES6 draft 15.13.7).
 * This API is experimental and may change significantly.
 */
class V8_EXPORT DataView : public ArrayBufferView {
    public:
        static Local<DataView> New(Local<ArrayBuffer> array_buffer,
                                   size_t byte_offset, size_t length);
        static Local<DataView> New(Local<SharedArrayBuffer> shared_array_buffer,
                                   size_t byte_offset, size_t length);
        V8_INLINE static DataView* Cast(Value* obj);

    private:
        DataView();
        static void CheckCast(Value* obj);
};


/**
 * An instance of the built-in SharedArrayBuffer constructor.
 * This API is experimental and may change significantly.
 */
class V8_EXPORT SharedArrayBuffer : public Object {
    public:
        /**
         * The contents of an |SharedArrayBuffer|. Externalization of
         * |SharedArrayBuffer| returns an instance of this class, populated, with a
         * pointer to data and byte length.
         *
         * The Data pointer of SharedArrayBuffer::Contents is always allocated with
         * |ArrayBuffer::Allocator::Allocate| by the allocator specified in
         * v8::Isolate::CreateParams::array_buffer_allocator.
         *
         * This API is experimental and may change significantly.
         */
        class V8_EXPORT Contents {  // NOLINT
            public:
                Contents() : data_(NULL), byte_length_(0) {}

                void* Data() const {
                    return data_;
                }
                size_t ByteLength() const {
                    return byte_length_;
                }

            private:
                void* data_;
                size_t byte_length_;

                friend class SharedArrayBuffer;
        };


        /**
         * Data length in bytes.
         */
        size_t ByteLength() const;

        /**
         * Create a new SharedArrayBuffer. Allocate |byte_length| bytes.
         * Allocated memory will be owned by a created SharedArrayBuffer and
         * will be deallocated when it is garbage-collected,
         * unless the object is externalized.
         */
        static Local<SharedArrayBuffer> New(Isolate* isolate, size_t byte_length);

        /**
         * Create a new SharedArrayBuffer over an existing memory block.  The created
         * array buffer is immediately in externalized state unless otherwise
         * specified. The memory block will not be reclaimed when a created
         * SharedArrayBuffer is garbage-collected.
         */
        static Local<SharedArrayBuffer> New(
            Isolate* isolate, void* data, size_t byte_length,
            ArrayBufferCreationMode mode = ArrayBufferCreationMode::kExternalized);

        /**
         * Returns true if SharedArrayBuffer is externalized, that is, does not
         * own its memory block.
         */
        bool IsExternal() const;

        /**
         * Make this SharedArrayBuffer external. The pointer to underlying memory
         * block and byte length are returned as |Contents| structure. After
         * SharedArrayBuffer had been externalized, it does no longer own the memory
         * block. The caller should take steps to free memory when it is no longer
         * needed.
         *
         * The memory block is guaranteed to be allocated with |Allocator::Allocate|
         * by the allocator specified in
         * v8::Isolate::CreateParams::array_buffer_allocator.
         *
         */
        Contents Externalize();

        /**
         * Get a pointer to the ArrayBuffer's underlying memory block without
         * externalizing it. If the ArrayBuffer is not externalized, this pointer
         * will become invalid as soon as the ArrayBuffer became garbage collected.
         *
         * The embedder should make sure to hold a strong reference to the
         * ArrayBuffer while accessing this pointer.
         *
         * The memory block is guaranteed to be allocated with |Allocator::Allocate|
         * by the allocator specified in
         * v8::Isolate::CreateParams::array_buffer_allocator.
         */
        Contents GetContents();

        V8_INLINE static SharedArrayBuffer* Cast(Value* obj);

        static const int kInternalFieldCount = V8_ARRAY_BUFFER_INTERNAL_FIELD_COUNT;

    private:
        SharedArrayBuffer();
        static void CheckCast(Value* obj);
};


/**
 * An instance of the built-in Date constructor (ECMA-262, 15.9).
 */
class V8_EXPORT Date : public Object {
    public:
        static V8_DEPRECATE_SOON("Use maybe version.",
                                 Local<Value> New(Isolate* isolate, double time));
        static V8_WARN_UNUSED_RESULT MaybeLocal<Value> New(Local<Context> context,
                double time);

        /**
         * A specialization of Value::NumberValue that is more efficient
         * because we know the structure of this object.
         */
        double ValueOf() const;

        V8_INLINE static Date* Cast(v8::Value* obj);

        /**
         * Notification that the embedder has changed the time zone,
         * daylight savings time, or other date / time configuration
         * parameters.  V8 keeps a cache of various values used for
         * date / time computation.  This notification will reset
         * those cached values for the current context so that date /
         * time configuration changes would be reflected in the Date
         * object.
         *
         * This API should not be called more than needed as it will
         * negatively impact the performance of date operations.
         */
        static void DateTimeConfigurationChangeNotification(Isolate* isolate);

    private:
        static void CheckCast(v8::Value* obj);
};


/**
 * A Number object (ECMA-262, 4.3.21).
 */
class V8_EXPORT NumberObject : public Object {
    public:
        static Local<Value> New(Isolate* isolate, double value);

        double ValueOf() const;

        V8_INLINE static NumberObject* Cast(v8::Value* obj);

    private:
        static void CheckCast(v8::Value* obj);
};


/**
 * A Boolean object (ECMA-262, 4.3.15).
 */
class V8_EXPORT BooleanObject : public Object {
    public:
        static Local<Value> New(Isolate* isolate, bool value);
        V8_DEPRECATED("Pass an isolate", static Local<Value> New(bool value));

        bool ValueOf() const;

        V8_INLINE static BooleanObject* Cast(v8::Value* obj);

    private:
        static void CheckCast(v8::Value* obj);
};


/**
 * A String object (ECMA-262, 4.3.18).
 */
class V8_EXPORT StringObject : public Object {
    public:
        static Local<Value> New(Local<String> value);

        Local<String> ValueOf() const;

        V8_INLINE static StringObject* Cast(v8::Value* obj);

    private:
        static void CheckCast(v8::Value* obj);
};


/**
 * A Symbol object (ECMA-262 edition 6).
 *
 * This is an experimental feature. Use at your own risk.
 */
class V8_EXPORT SymbolObject : public Object {
    public:
        static Local<Value> New(Isolate* isolate, Local<Symbol> value);

        Local<Symbol> ValueOf() const;

        V8_INLINE static SymbolObject* Cast(v8::Value* obj);

    private:
        static void CheckCast(v8::Value* obj);
};


/**
 * An instance of the built-in RegExp constructor (ECMA-262, 15.10).
 */
class V8_EXPORT RegExp : public Object {
    public:
        /**
         * Regular expression flag bits. They can be or'ed to enable a set
         * of flags.
         */
        enum Flags {
            kNone = 0,
            kGlobal = 1,
            kIgnoreCase = 2,
            kMultiline = 4,
            kSticky = 8,
            kUnicode = 16
        };

        /**
         * Creates a regular expression from the given pattern string and
         * the flags bit field. May throw a JavaScript exception as
         * described in ECMA-262, 15.10.4.1.
         *
         * For example,
         *   RegExp::New(v8::String::New("foo"),
         *               static_cast<RegExp::Flags>(kGlobal | kMultiline))
         * is equivalent to evaluating "/foo/gm".
         */
        static V8_DEPRECATE_SOON("Use maybe version",
                                 Local<RegExp> New(Local<String> pattern,
                                         Flags flags));
        static V8_WARN_UNUSED_RESULT MaybeLocal<RegExp> New(Local<Context> context,
                Local<String> pattern,
                Flags flags);

        /**
         * Returns the value of the source property: a string representing
         * the regular expression.
         */
        Local<String> GetSource() const;

        /**
         * Returns the flags bit field.
         */
        Flags GetFlags() const;

        V8_INLINE static RegExp* Cast(v8::Value* obj);

    private:
        static void CheckCast(v8::Value* obj);
};


/**
 * A JavaScript value that wraps a C++ void*. This type of value is mainly used
 * to associate C++ data structures with JavaScript objects.
 */
class V8_EXPORT External : public Value {
    public:
        static Local<External> New(Isolate* isolate, void* value);
        V8_INLINE static External* Cast(Value* obj);
        void* Value() const;
    private:
        static void CheckCast(v8::Value* obj);
};


#define V8_INTRINSICS_LIST(F) F(ArrayProto_values, array_values_iterator)

enum Intrinsic {
#define V8_DECL_INTRINSIC(name, iname) k##name,
    V8_INTRINSICS_LIST(V8_DECL_INTRINSIC)
#undef V8_DECL_INTRINSIC
};


// --- Templates ---


/**
 * The superclass of object and function templates.
 */
class V8_EXPORT Template : public Data {
    public:
        /**
         * Adds a property to each instance created by this template.
         *
         * The property must be defined either as a primitive value, or a template.
         */
        void Set(Local<Name> name, Local<Data> value,
                 PropertyAttribute attributes = None);
        V8_INLINE void Set(Isolate* isolate, const char* name, Local<Data> value);

        void SetAccessorProperty(
            Local<Name> name,
            Local<FunctionTemplate> getter = Local<FunctionTemplate>(),
            Local<FunctionTemplate> setter = Local<FunctionTemplate>(),
            PropertyAttribute attribute = None,
            AccessControl settings = DEFAULT);

        /**
         * Whenever the property with the given name is accessed on objects
         * created from this Template the getter and setter callbacks
         * are called instead of getting and setting the property directly
         * on the JavaScript object.
         *
         * \param name The name of the property for which an accessor is added.
         * \param getter The callback to invoke when getting the property.
         * \param setter The callback to invoke when setting the property.
         * \param data A piece of data that will be passed to the getter and setter
         *   callbacks whenever they are invoked.
         * \param settings Access control settings for the accessor. This is a bit
         *   field consisting of one of more of
         *   DEFAULT = 0, ALL_CAN_READ = 1, or ALL_CAN_WRITE = 2.
         *   The default is to not allow cross-context access.
         *   ALL_CAN_READ means that all cross-context reads are allowed.
         *   ALL_CAN_WRITE means that all cross-context writes are allowed.
         *   The combination ALL_CAN_READ | ALL_CAN_WRITE can be used to allow all
         *   cross-context access.
         * \param attribute The attributes of the property for which an accessor
         *   is added.
         * \param signature The signature describes valid receivers for the accessor
         *   and is used to perform implicit instance checks against them. If the
         *   receiver is incompatible (i.e. is not an instance of the constructor as
         *   defined by FunctionTemplate::HasInstance()), an implicit TypeError is
         *   thrown and no callback is invoked.
         */
        void SetNativeDataProperty(
            Local<String> name, AccessorGetterCallback getter,
            AccessorSetterCallback setter = 0,
            // TODO(dcarney): gcc can't handle Local below
            Local<Value> data = Local<Value>(), PropertyAttribute attribute = None,
            Local<AccessorSignature> signature = Local<AccessorSignature>(),
            AccessControl settings = DEFAULT);
        void SetNativeDataProperty(
            Local<Name> name, AccessorNameGetterCallback getter,
            AccessorNameSetterCallback setter = 0,
            // TODO(dcarney): gcc can't handle Local below
            Local<Value> data = Local<Value>(), PropertyAttribute attribute = None,
            Local<AccessorSignature> signature = Local<AccessorSignature>(),
            AccessControl settings = DEFAULT);

        /**
         * During template instantiation, sets the value with the intrinsic property
         * from the correct context.
         */
        void SetIntrinsicDataProperty(Local<Name> name, Intrinsic intrinsic,
                                      PropertyAttribute attribute = None);

    private:
        Template();

        friend class ObjectTemplate;
        friend class FunctionTemplate;
};


/**
 * NamedProperty[Getter|Setter] are used as interceptors on object.
 * See ObjectTemplate::SetNamedPropertyHandler.
 */
typedef void (*NamedPropertyGetterCallback)(
    Local<String> property,
    const PropertyCallbackInfo<Value>& info);


/**
 * Returns the value if the setter intercepts the request.
 * Otherwise, returns an empty handle.
 */
typedef void (*NamedPropertySetterCallback)(
    Local<String> property,
    Local<Value> value,
    const PropertyCallbackInfo<Value>& info);


/**
 * Returns a non-empty handle if the interceptor intercepts the request.
 * The result is an integer encoding property attributes (like v8::None,
 * v8::DontEnum, etc.)
 */
typedef void (*NamedPropertyQueryCallback)(
    Local<String> property,
    const PropertyCallbackInfo<Integer>& info);


/**
 * Returns a non-empty handle if the deleter intercepts the request.
 * The return value is true if the property could be deleted and false
 * otherwise.
 */
typedef void (*NamedPropertyDeleterCallback)(
    Local<String> property,
    const PropertyCallbackInfo<Boolean>& info);


/**
 * Returns an array containing the names of the properties the named
 * property getter intercepts.
 */
typedef void (*NamedPropertyEnumeratorCallback)(
    const PropertyCallbackInfo<Array>& info);


// TODO(dcarney): Deprecate and remove previous typedefs, and replace
// GenericNamedPropertyFooCallback with just NamedPropertyFooCallback.

/**
 * Interceptor for get requests on an object.
 *
 * Use `info.GetReturnValue().Set()` to set the return value of the
 * intercepted get request.
 *
 * \param property The name of the property for which the request was
 * intercepted.
 * \param info Information about the intercepted request, such as
 * isolate, receiver, return value, or whether running in `'use strict`' mode.
 * See `PropertyCallbackInfo`.
 *
 * \code
 *  void GetterCallback(
 *    Local<Name> name,
 *    const v8::PropertyCallbackInfo<v8::Value>& info) {
 *      info.GetReturnValue().Set(v8_num(42));
 *  }
 *
 *  v8::Local<v8::FunctionTemplate> templ =
 *      v8::FunctionTemplate::New(isolate);
 *  templ->InstanceTemplate()->SetHandler(
 *      v8::NamedPropertyHandlerConfiguration(GetterCallback));
 *  LocalContext env;
 *  env->Global()
 *      ->Set(env.local(), v8_str("obj"), templ->GetFunction(env.local())
 *                                             .ToLocalChecked()
 *                                             ->NewInstance(env.local())
 *                                             .ToLocalChecked())
 *      .FromJust();
 *  v8::Local<v8::Value> result = CompileRun("obj.a = 17; obj.a");
 *  CHECK(v8_num(42)->Equals(env.local(), result).FromJust());
 * \endcode
 *
 * See also `ObjectTemplate::SetHandler`.
 */
typedef void (*GenericNamedPropertyGetterCallback)(
    Local<Name> property, const PropertyCallbackInfo<Value>& info);

/**
 * Interceptor for set requests on an object.
 *
 * Use `info.GetReturnValue()` to indicate whether the request was intercepted
 * or not. If the setter successfully intercepts the request, i.e., if the
 * request should not be further executed, call
 * `info.GetReturnValue().Set(value)`. If the setter
 * did not intercept the request, i.e., if the request should be handled as
 * if no interceptor is present, do not not call `Set()`.
 *
 * \param property The name of the property for which the request was
 * intercepted.
 * \param value The value which the property will have if the request
 * is not intercepted.
 * \param info Information about the intercepted request, such as
 * isolate, receiver, return value, or whether running in `'use strict'` mode.
 * See `PropertyCallbackInfo`.
 *
 * See also
 * `ObjectTemplate::SetHandler.`
 */
typedef void (*GenericNamedPropertySetterCallback)(
    Local<Name> property, Local<Value> value,
    const PropertyCallbackInfo<Value>& info);

/**
 * Intercepts all requests that query the attributes of the
 * property, e.g., getOwnPropertyDescriptor(), propertyIsEnumerable(), and
 * defineProperty().
 *
 * Use `info.GetReturnValue().Set(value)` to set the property attributes. The
 * value is an interger encoding a `v8::PropertyAttribute`.
 *
 * \param property The name of the property for which the request was
 * intercepted.
 * \param info Information about the intercepted request, such as
 * isolate, receiver, return value, or whether running in `'use strict'` mode.
 * See `PropertyCallbackInfo`.
 *
 * \note Some functions query the property attributes internally, even though
 * they do not return the attributes. For example, `hasOwnProperty()` can
 * trigger this interceptor depending on the state of the object.
 *
 * See also
 * `ObjectTemplate::SetHandler.`
 */
typedef void (*GenericNamedPropertyQueryCallback)(
    Local<Name> property, const PropertyCallbackInfo<Integer>& info);

/**
 * Interceptor for delete requests on an object.
 *
 * Use `info.GetReturnValue()` to indicate whether the request was intercepted
 * or not. If the deleter successfully intercepts the request, i.e., if the
 * request should not be further executed, call
 * `info.GetReturnValue().Set(value)` with a boolean `value`. The `value` is
 * used as the return value of `delete`.
 *
 * \param property The name of the property for which the request was
 * intercepted.
 * \param info Information about the intercepted request, such as
 * isolate, receiver, return value, or whether running in `'use strict'` mode.
 * See `PropertyCallbackInfo`.
 *
 * \note If you need to mimic the behavior of `delete`, i.e., throw in strict
 * mode instead of returning false, use `info.ShouldThrowOnError()` to determine
 * if you are in strict mode.
 *
 * See also `ObjectTemplate::SetHandler.`
 */
typedef void (*GenericNamedPropertyDeleterCallback)(
    Local<Name> property, const PropertyCallbackInfo<Boolean>& info);


/**
 * Returns an array containing the names of the properties the named
 * property getter intercepts.
 */
typedef void (*GenericNamedPropertyEnumeratorCallback)(
    const PropertyCallbackInfo<Array>& info);

/**
 * Interceptor for defineProperty requests on an object.
 *
 * Use `info.GetReturnValue()` to indicate whether the request was intercepted
 * or not. If the definer successfully intercepts the request, i.e., if the
 * request should not be further executed, call
 * `info.GetReturnValue().Set(value)`. If the definer
 * did not intercept the request, i.e., if the request should be handled as
 * if no interceptor is present, do not not call `Set()`.
 *
 * \param property The name of the property for which the request was
 * intercepted.
 * \param desc The property descriptor which is used to define the
 * property if the request is not intercepted.
 * \param info Information about the intercepted request, such as
 * isolate, receiver, return value, or whether running in `'use strict'` mode.
 * See `PropertyCallbackInfo`.
 *
 * See also `ObjectTemplate::SetHandler`.
 */
typedef void (*GenericNamedPropertyDefinerCallback)(
    Local<Name> property, const PropertyDescriptor& desc,
    const PropertyCallbackInfo<Value>& info);

/**
 * Interceptor for getOwnPropertyDescriptor requests on an object.
 *
 * Use `info.GetReturnValue().Set()` to set the return value of the
 * intercepted request. The return value must be an object that
 * can be converted to a PropertyDescriptor, e.g., a `v8::value` returned from
 * `v8::Object::getOwnPropertyDescriptor`.
 *
 * \param property The name of the property for which the request was
 * intercepted.
 * \info Information about the intercepted request, such as
 * isolate, receiver, return value, or whether running in `'use strict'` mode.
 * See `PropertyCallbackInfo`.
 *
 * \note If GetOwnPropertyDescriptor is intercepted, it will
 * always return true, i.e., indicate that the property was found.
 *
 * See also `ObjectTemplate::SetHandler`.
 */
typedef void (*GenericNamedPropertyDescriptorCallback)(
    Local<Name> property, const PropertyCallbackInfo<Value>& info);

/**
 * See `v8::GenericNamedPropertyGetterCallback`.
 */
typedef void (*IndexedPropertyGetterCallback)(
    uint32_t index,
    const PropertyCallbackInfo<Value>& info);

/**
 * See `v8::GenericNamedPropertySetterCallback`.
 */
typedef void (*IndexedPropertySetterCallback)(
    uint32_t index,
    Local<Value> value,
    const PropertyCallbackInfo<Value>& info);

/**
 * See `v8::GenericNamedPropertyQueryCallback`.
 */
typedef void (*IndexedPropertyQueryCallback)(
    uint32_t index,
    const PropertyCallbackInfo<Integer>& info);

/**
 * See `v8::GenericNamedPropertyDeleterCallback`.
 */
typedef void (*IndexedPropertyDeleterCallback)(
    uint32_t index,
    const PropertyCallbackInfo<Boolean>& info);

/**
 * See `v8::GenericNamedPropertyEnumeratorCallback`.
 */
typedef void (*IndexedPropertyEnumeratorCallback)(
    const PropertyCallbackInfo<Array>& info);

/**
 * See `v8::GenericNamedPropertyDefinerCallback`.
 */
typedef void (*IndexedPropertyDefinerCallback)(
    uint32_t index, const PropertyDescriptor& desc,
    const PropertyCallbackInfo<Value>& info);

/**
 * See `v8::GenericNamedPropertyDescriptorCallback`.
 */
typedef void (*IndexedPropertyDescriptorCallback)(
    uint32_t index, const PropertyCallbackInfo<Value>& info);

/**
 * Access type specification.
 */
enum AccessType {
    ACCESS_GET,
    ACCESS_SET,
    ACCESS_HAS,
    ACCESS_DELETE,
    ACCESS_KEYS
};


/**
 * Returns true if the given context should be allowed to access the given
 * object.
 */
typedef bool (*AccessCheckCallback)(Local<Context> accessing_context,
                                    Local<Object> accessed_object,
                                    Local<Value> data);

/**
 * A FunctionTemplate is used to create functions at runtime. There
 * can only be one function created from a FunctionTemplate in a
 * context.  The lifetime of the created function is equal to the
 * lifetime of the context.  So in case the embedder needs to create
 * temporary functions that can be collected using Scripts is
 * preferred.
 *
 * Any modification of a FunctionTemplate after first instantiation will trigger
 * a crash.
 *
 * A FunctionTemplate can have properties, these properties are added to the
 * function object when it is created.
 *
 * A FunctionTemplate has a corresponding instance template which is
 * used to create object instances when the function is used as a
 * constructor. Properties added to the instance template are added to
 * each object instance.
 *
 * A FunctionTemplate can have a prototype template. The prototype template
 * is used to create the prototype object of the function.
 *
 * The following example shows how to use a FunctionTemplate:
 *
 * \code
 *    v8::Local<v8::FunctionTemplate> t = v8::FunctionTemplate::New(isolate);
 *    t->Set(isolate, "func_property", v8::Number::New(isolate, 1));
 *
 *    v8::Local<v8::Template> proto_t = t->PrototypeTemplate();
 *    proto_t->Set(isolate,
 *                 "proto_method",
 *                 v8::FunctionTemplate::New(isolate, InvokeCallback));
 *    proto_t->Set(isolate, "proto_const", v8::Number::New(isolate, 2));
 *
 *    v8::Local<v8::ObjectTemplate> instance_t = t->InstanceTemplate();
 *    instance_t->SetAccessor(String::NewFromUtf8(isolate, "instance_accessor"),
 *                            InstanceAccessorCallback);
 *    instance_t->SetNamedPropertyHandler(PropertyHandlerCallback);
 *    instance_t->Set(String::NewFromUtf8(isolate, "instance_property"),
 *                    Number::New(isolate, 3));
 *
 *    v8::Local<v8::Function> function = t->GetFunction();
 *    v8::Local<v8::Object> instance = function->NewInstance();
 * \endcode
 *
 * Let's use "function" as the JS variable name of the function object
 * and "instance" for the instance object created above.  The function
 * and the instance will have the following properties:
 *
 * \code
 *   func_property in function == true;
 *   function.func_property == 1;
 *
 *   function.prototype.proto_method() invokes 'InvokeCallback'
 *   function.prototype.proto_const == 2;
 *
 *   instance instanceof function == true;
 *   instance.instance_accessor calls 'InstanceAccessorCallback'
 *   instance.instance_property == 3;
 * \endcode
 *
 * A FunctionTemplate can inherit from another one by calling the
 * FunctionTemplate::Inherit method.  The following graph illustrates
 * the semantics of inheritance:
 *
 * \code
 *   FunctionTemplate Parent  -> Parent() . prototype -> { }
 *     ^                                                  ^
 *     | Inherit(Parent)                                  | .__proto__
 *     |                                                  |
 *   FunctionTemplate Child   -> Child()  . prototype -> { }
 * \endcode
 *
 * A FunctionTemplate 'Child' inherits from 'Parent', the prototype
 * object of the Child() function has __proto__ pointing to the
 * Parent() function's prototype object. An instance of the Child
 * function has all properties on Parent's instance templates.
 *
 * Let Parent be the FunctionTemplate initialized in the previous
 * section and create a Child FunctionTemplate by:
 *
 * \code
 *   Local<FunctionTemplate> parent = t;
 *   Local<FunctionTemplate> child = FunctionTemplate::New();
 *   child->Inherit(parent);
 *
 *   Local<Function> child_function = child->GetFunction();
 *   Local<Object> child_instance = child_function->NewInstance();
 * \endcode
 *
 * The Child function and Child instance will have the following
 * properties:
 *
 * \code
 *   child_func.prototype.__proto__ == function.prototype;
 *   child_instance.instance_accessor calls 'InstanceAccessorCallback'
 *   child_instance.instance_property == 3;
 * \endcode
 */
class V8_EXPORT FunctionTemplate : public Template {
    public:
        /** Creates a function template.*/
        static Local<FunctionTemplate> New(
            Isolate* isolate, FunctionCallback callback = 0,
            Local<Value> data = Local<Value>(),
            Local<Signature> signature = Local<Signature>(), int length = 0,
            ConstructorBehavior behavior = ConstructorBehavior::kAllow);

        /** Get a template included in the snapshot by index. */
        static MaybeLocal<FunctionTemplate> FromSnapshot(Isolate* isolate,
                size_t index);

        /**
         * Creates a function template with a fast handler. If a fast handler is set,
         * the callback cannot be null.
         */
        static Local<FunctionTemplate> NewWithFastHandler(
            Isolate* isolate, FunctionCallback callback,
            experimental::FastAccessorBuilder* fast_handler = nullptr,
            Local<Value> data = Local<Value>(),
            Local<Signature> signature = Local<Signature>(), int length = 0);

        /** Returns the unique function instance in the current execution context.*/
        V8_DEPRECATE_SOON("Use maybe version", Local<Function> GetFunction());
        V8_WARN_UNUSED_RESULT MaybeLocal<Function> GetFunction(
            Local<Context> context);

        /**
         * Similar to Context::NewRemoteContext, this creates an instance that
         * isn't backed by an actual object.
         *
         * The InstanceTemplate of this FunctionTemplate must have access checks with
         * handlers installed.
         */
        V8_WARN_UNUSED_RESULT MaybeLocal<Object> NewRemoteInstance();

        /**
         * Set the call-handler callback for a FunctionTemplate.  This
         * callback is called whenever the function created from this
         * FunctionTemplate is called.
         */
        void SetCallHandler(
            FunctionCallback callback, Local<Value> data = Local<Value>(),
            experimental::FastAccessorBuilder* fast_handler = nullptr);

        /** Set the predefined length property for the FunctionTemplate. */
        void SetLength(int length);

        /** Get the InstanceTemplate. */
        Local<ObjectTemplate> InstanceTemplate();

        /** Causes the function template to inherit from a parent function template.*/
        void Inherit(Local<FunctionTemplate> parent);

        /**
         * A PrototypeTemplate is the template used to create the prototype object
         * of the function created by this template.
         */
        Local<ObjectTemplate> PrototypeTemplate();

        /**
         * Set the class name of the FunctionTemplate.  This is used for
         * printing objects created with the function created from the
         * FunctionTemplate as its constructor.
         */
        void SetClassName(Local<String> name);


        /**
         * When set to true, no access check will be performed on the receiver of a
         * function call.  Currently defaults to true, but this is subject to change.
         */
        void SetAcceptAnyReceiver(bool value);

        /**
         * Determines whether the __proto__ accessor ignores instances of
         * the function template.  If instances of the function template are
         * ignored, __proto__ skips all instances and instead returns the
         * next object in the prototype chain.
         *
         * Call with a value of true to make the __proto__ accessor ignore
         * instances of the function template.  Call with a value of false
         * to make the __proto__ accessor not ignore instances of the
         * function template.  By default, instances of a function template
         * are not ignored.
         */
        void SetHiddenPrototype(bool value);

        /**
         * Sets the ReadOnly flag in the attributes of the 'prototype' property
         * of functions created from this FunctionTemplate to true.
         */
        void ReadOnlyPrototype();

        /**
         * Removes the prototype property from functions created from this
         * FunctionTemplate.
         */
        void RemovePrototype();

        /**
         * Returns true if the given object is an instance of this function
         * template.
         */
        bool HasInstance(Local<Value> object);

    private:
        FunctionTemplate();
        friend class Context;
        friend class ObjectTemplate;
};

/**
 * Configuration flags for v8::NamedPropertyHandlerConfiguration or
 * v8::IndexedPropertyHandlerConfiguration.
 */
enum class PropertyHandlerFlags {
    /**
     * None.
     */
    kNone = 0,

    /**
     * See ALL_CAN_READ above.
     */
    kAllCanRead = 1,

    /** Will not call into interceptor for properties on the receiver or prototype
     * chain, i.e., only call into interceptor for properties that do not exist.
     * Currently only valid for named interceptors.
     */
    kNonMasking = 1 << 1,

    /**
     * Will not call into interceptor for symbol lookup.  Only meaningful for
     * named interceptors.
     */
    kOnlyInterceptStrings = 1 << 2,
};

struct NamedPropertyHandlerConfiguration {
    NamedPropertyHandlerConfiguration(
        /** Note: getter is required */
        GenericNamedPropertyGetterCallback getter = 0,
        GenericNamedPropertySetterCallback setter = 0,
        GenericNamedPropertyQueryCallback query = 0,
        GenericNamedPropertyDeleterCallback deleter = 0,
        GenericNamedPropertyEnumeratorCallback enumerator = 0,
        Local<Value> data = Local<Value>(),
        PropertyHandlerFlags flags = PropertyHandlerFlags::kNone)
        : getter(getter),
          setter(setter),
          query(query),
          deleter(deleter),
          enumerator(enumerator),
          definer(0),
          descriptor(0),
          data(data),
          flags(flags) {}

    NamedPropertyHandlerConfiguration(
        GenericNamedPropertyGetterCallback getter,
        GenericNamedPropertySetterCallback setter,
        GenericNamedPropertyDescriptorCallback descriptor,
        GenericNamedPropertyDeleterCallback deleter,
        GenericNamedPropertyEnumeratorCallback enumerator,
        GenericNamedPropertyDefinerCallback definer,
        Local<Value> data = Local<Value>(),
        PropertyHandlerFlags flags = PropertyHandlerFlags::kNone)
        : getter(getter),
          setter(setter),
          query(0),
          deleter(deleter),
          enumerator(enumerator),
          definer(definer),
          descriptor(descriptor),
          data(data),
          flags(flags) {}

    GenericNamedPropertyGetterCallback getter;
    GenericNamedPropertySetterCallback setter;
    GenericNamedPropertyQueryCallback query;
    GenericNamedPropertyDeleterCallback deleter;
    GenericNamedPropertyEnumeratorCallback enumerator;
    GenericNamedPropertyDefinerCallback definer;
    GenericNamedPropertyDescriptorCallback descriptor;
    Local<Value> data;
    PropertyHandlerFlags flags;
};


struct IndexedPropertyHandlerConfiguration {
    IndexedPropertyHandlerConfiguration(
        /** Note: getter is required */
        IndexedPropertyGetterCallback getter = 0,
        IndexedPropertySetterCallback setter = 0,
        IndexedPropertyQueryCallback query = 0,
        IndexedPropertyDeleterCallback deleter = 0,
        IndexedPropertyEnumeratorCallback enumerator = 0,
        Local<Value> data = Local<Value>(),
        PropertyHandlerFlags flags = PropertyHandlerFlags::kNone)
        : getter(getter),
          setter(setter),
          query(query),
          deleter(deleter),
          enumerator(enumerator),
          definer(0),
          descriptor(0),
          data(data),
          flags(flags) {}

    IndexedPropertyHandlerConfiguration(
        IndexedPropertyGetterCallback getter,
        IndexedPropertySetterCallback setter,
        IndexedPropertyDescriptorCallback descriptor,
        IndexedPropertyDeleterCallback deleter,
        IndexedPropertyEnumeratorCallback enumerator,
        IndexedPropertyDefinerCallback definer,
        Local<Value> data = Local<Value>(),
        PropertyHandlerFlags flags = PropertyHandlerFlags::kNone)
        : getter(getter),
          setter(setter),
          query(0),
          deleter(deleter),
          enumerator(enumerator),
          definer(definer),
          descriptor(descriptor),
          data(data),
          flags(flags) {}

    IndexedPropertyGetterCallback getter;
    IndexedPropertySetterCallback setter;
    IndexedPropertyQueryCallback query;
    IndexedPropertyDeleterCallback deleter;
    IndexedPropertyEnumeratorCallback enumerator;
    IndexedPropertyDefinerCallback definer;
    IndexedPropertyDescriptorCallback descriptor;
    Local<Value> data;
    PropertyHandlerFlags flags;
};


/**
 * An ObjectTemplate is used to create objects at runtime.
 *
 * Properties added to an ObjectTemplate are added to each object
 * created from the ObjectTemplate.
 */
class V8_EXPORT ObjectTemplate : public Template {
    public:
        /** Creates an ObjectTemplate. */
        static Local<ObjectTemplate> New(
            Isolate* isolate,
            Local<FunctionTemplate> constructor = Local<FunctionTemplate>());
        static V8_DEPRECATED("Use isolate version", Local<ObjectTemplate> New());

        /** Get a template included in the snapshot by index. */
        static MaybeLocal<ObjectTemplate> FromSnapshot(Isolate* isolate,
                size_t index);

        /** Creates a new instance of this template.*/
        V8_DEPRECATE_SOON("Use maybe version", Local<Object> NewInstance());
        V8_WARN_UNUSED_RESULT MaybeLocal<Object> NewInstance(Local<Context> context);

        /**
         * Sets an accessor on the object template.
         *
         * Whenever the property with the given name is accessed on objects
         * created from this ObjectTemplate the getter and setter callbacks
         * are called instead of getting and setting the property directly
         * on the JavaScript object.
         *
         * \param name The name of the property for which an accessor is added.
         * \param getter The callback to invoke when getting the property.
         * \param setter The callback to invoke when setting the property.
         * \param data A piece of data that will be passed to the getter and setter
         *   callbacks whenever they are invoked.
         * \param settings Access control settings for the accessor. This is a bit
         *   field consisting of one of more of
         *   DEFAULT = 0, ALL_CAN_READ = 1, or ALL_CAN_WRITE = 2.
         *   The default is to not allow cross-context access.
         *   ALL_CAN_READ means that all cross-context reads are allowed.
         *   ALL_CAN_WRITE means that all cross-context writes are allowed.
         *   The combination ALL_CAN_READ | ALL_CAN_WRITE can be used to allow all
         *   cross-context access.
         * \param attribute The attributes of the property for which an accessor
         *   is added.
         * \param signature The signature describes valid receivers for the accessor
         *   and is used to perform implicit instance checks against them. If the
         *   receiver is incompatible (i.e. is not an instance of the constructor as
         *   defined by FunctionTemplate::HasInstance()), an implicit TypeError is
         *   thrown and no callback is invoked.
         */
        void SetAccessor(
            Local<String> name, AccessorGetterCallback getter,
            AccessorSetterCallback setter = 0, Local<Value> data = Local<Value>(),
            AccessControl settings = DEFAULT, PropertyAttribute attribute = None,
            Local<AccessorSignature> signature = Local<AccessorSignature>());
        void SetAccessor(
            Local<Name> name, AccessorNameGetterCallback getter,
            AccessorNameSetterCallback setter = 0, Local<Value> data = Local<Value>(),
            AccessControl settings = DEFAULT, PropertyAttribute attribute = None,
            Local<AccessorSignature> signature = Local<AccessorSignature>());

        /**
         * Sets a named property handler on the object template.
         *
         * Whenever a property whose name is a string is accessed on objects created
         * from this object template, the provided callback is invoked instead of
         * accessing the property directly on the JavaScript object.
         *
         * SetNamedPropertyHandler() is different from SetHandler(), in
         * that the latter can intercept symbol-named properties as well as
         * string-named properties when called with a
         * NamedPropertyHandlerConfiguration. New code should use SetHandler().
         *
         * \param getter The callback to invoke when getting a property.
         * \param setter The callback to invoke when setting a property.
         * \param query The callback to invoke to check if a property is present,
         *   and if present, get its attributes.
         * \param deleter The callback to invoke when deleting a property.
         * \param enumerator The callback to invoke to enumerate all the named
         *   properties of an object.
         * \param data A piece of data that will be passed to the callbacks
         *   whenever they are invoked.
         */
        // TODO(dcarney): deprecate
        void SetNamedPropertyHandler(NamedPropertyGetterCallback getter,
                                     NamedPropertySetterCallback setter = 0,
                                     NamedPropertyQueryCallback query = 0,
                                     NamedPropertyDeleterCallback deleter = 0,
                                     NamedPropertyEnumeratorCallback enumerator = 0,
                                     Local<Value> data = Local<Value>());

        /**
         * Sets a named property handler on the object template.
         *
         * Whenever a property whose name is a string or a symbol is accessed on
         * objects created from this object template, the provided callback is
         * invoked instead of accessing the property directly on the JavaScript
         * object.
         *
         * @param configuration The NamedPropertyHandlerConfiguration that defines the
         * callbacks to invoke when accessing a property.
         */
        void SetHandler(const NamedPropertyHandlerConfiguration& configuration);

        /**
         * Sets an indexed property handler on the object template.
         *
         * Whenever an indexed property is accessed on objects created from
         * this object template, the provided callback is invoked instead of
         * accessing the property directly on the JavaScript object.
         *
         * \param getter The callback to invoke when getting a property.
         * \param setter The callback to invoke when setting a property.
         * \param query The callback to invoke to check if an object has a property.
         * \param deleter The callback to invoke when deleting a property.
         * \param enumerator The callback to invoke to enumerate all the indexed
         *   properties of an object.
         * \param data A piece of data that will be passed to the callbacks
         *   whenever they are invoked.
         */
        // TODO(dcarney): deprecate
        void SetIndexedPropertyHandler(
            IndexedPropertyGetterCallback getter,
            IndexedPropertySetterCallback setter = 0,
            IndexedPropertyQueryCallback query = 0,
            IndexedPropertyDeleterCallback deleter = 0,
            IndexedPropertyEnumeratorCallback enumerator = 0,
            Local<Value> data = Local<Value>()) {
            SetHandler(IndexedPropertyHandlerConfiguration(getter, setter, query,
                       deleter, enumerator, data));
        }

        /**
         * Sets an indexed property handler on the object template.
         *
         * Whenever an indexed property is accessed on objects created from
         * this object template, the provided callback is invoked instead of
         * accessing the property directly on the JavaScript object.
         *
         * @param configuration The IndexedPropertyHandlerConfiguration that defines
         * the callbacks to invoke when accessing a property.
         */
        void SetHandler(const IndexedPropertyHandlerConfiguration& configuration);

        /**
         * Sets the callback to be used when calling instances created from
         * this template as a function.  If no callback is set, instances
         * behave like normal JavaScript objects that cannot be called as a
         * function.
         */
        void SetCallAsFunctionHandler(FunctionCallback callback,
                                      Local<Value> data = Local<Value>());

        /**
         * Mark object instances of the template as undetectable.
         *
         * In many ways, undetectable objects behave as though they are not
         * there.  They behave like 'undefined' in conditionals and when
         * printed.  However, properties can be accessed and called as on
         * normal objects.
         */
        void MarkAsUndetectable();

        /**
         * Sets access check callback on the object template and enables access
         * checks.
         *
         * When accessing properties on instances of this object template,
         * the access check callback will be called to determine whether or
         * not to allow cross-context access to the properties.
         */
        void SetAccessCheckCallback(AccessCheckCallback callback,
                                    Local<Value> data = Local<Value>());

        /**
         * Like SetAccessCheckCallback but invokes an interceptor on failed access
         * checks instead of looking up all-can-read properties. You can only use
         * either this method or SetAccessCheckCallback, but not both at the same
         * time.
         */
        void SetAccessCheckCallbackAndHandler(
            AccessCheckCallback callback,
            const NamedPropertyHandlerConfiguration& named_handler,
            const IndexedPropertyHandlerConfiguration& indexed_handler,
            Local<Value> data = Local<Value>());

        /**
         * Gets the number of internal fields for objects generated from
         * this template.
         */
        int InternalFieldCount();

        /**
         * Sets the number of internal fields for objects generated from
         * this template.
         */
        void SetInternalFieldCount(int value);

        /**
         * Returns true if the object will be an immutable prototype exotic object.
         */
        bool IsImmutableProto();

        /**
         * Makes the ObjectTempate for an immutable prototype exotic object, with an
         * immutable __proto__.
         */
        void SetImmutableProto();

    private:
        ObjectTemplate();
        static Local<ObjectTemplate> New(internal::Isolate* isolate,
                                         Local<FunctionTemplate> constructor);
        friend class FunctionTemplate;
};


/**
 * A Signature specifies which receiver is valid for a function.
 */
class V8_EXPORT Signature : public Data {
    public:
        static Local<Signature> New(
            Isolate* isolate,
            Local<FunctionTemplate> receiver = Local<FunctionTemplate>());

    private:
        Signature();
};


/**
 * An AccessorSignature specifies which receivers are valid parameters
 * to an accessor callback.
 */
class V8_EXPORT AccessorSignature : public Data {
    public:
        static Local<AccessorSignature> New(
            Isolate* isolate,
            Local<FunctionTemplate> receiver = Local<FunctionTemplate>());

    private:
        AccessorSignature();
};


// --- Extensions ---

class V8_EXPORT ExternalOneByteStringResourceImpl
    : public String::ExternalOneByteStringResource {
    public:
        ExternalOneByteStringResourceImpl() : data_(0), length_(0) {}
        ExternalOneByteStringResourceImpl(const char* data, size_t length)
            : data_(data), length_(length) {}
        const char* data() const {
            return data_;
        }
        size_t length() const {
            return length_;
        }

    private:
        const char* data_;
        size_t length_;
};

/**
 * Ignore
 */
class V8_EXPORT Extension {  // NOLINT
    public:
        // Note that the strings passed into this constructor must live as long
        // as the Extension itself.
        Extension(const char* name,
                  const char* source = 0,
                  int dep_count = 0,
                  const char** deps = 0,
                  int source_length = -1);
        virtual ~Extension() { }
        virtual v8::Local<v8::FunctionTemplate> GetNativeFunctionTemplate(
            v8::Isolate* isolate, v8::Local<v8::String> name) {
            return v8::Local<v8::FunctionTemplate>();
        }

        const char* name() const {
            return name_;
        }
        size_t source_length() const {
            return source_length_;
        }
        const String::ExternalOneByteStringResource* source() const {
            return &source_;
        }
        int dependency_count() {
            return dep_count_;
        }
        const char** dependencies() {
            return deps_;
        }
        void set_auto_enable(bool value) {
            auto_enable_ = value;
        }
        bool auto_enable() {
            return auto_enable_;
        }

        // Disallow copying and assigning.
        Extension(const Extension&) = delete;
        void operator=(const Extension&) = delete;

    private:
        const char* name_;
        size_t source_length_;  // expected to initialize before source_
        ExternalOneByteStringResourceImpl source_;
        int dep_count_;
        const char** deps_;
        bool auto_enable_;
};


void V8_EXPORT RegisterExtension(Extension* extension);


// --- Statics ---

V8_INLINE Local<Primitive> Undefined(Isolate* isolate);
V8_INLINE Local<Primitive> Null(Isolate* isolate);
V8_INLINE Local<Boolean> True(Isolate* isolate);
V8_INLINE Local<Boolean> False(Isolate* isolate);

/**
 * A set of constraints that specifies the limits of the runtime's memory use.
 * You must set the heap size before initializing the VM - the size cannot be
 * adjusted after the VM is initialized.
 *
 * If you are using threads then you should hold the V8::Locker lock while
 * setting the stack limit and you must set a non-default stack limit separately
 * for each thread.
 *
 * The arguments for set_max_semi_space_size, set_max_old_space_size,
 * set_max_executable_size, set_code_range_size specify limits in MB.
 */
class V8_EXPORT ResourceConstraints {
    public:
        ResourceConstraints();

        /**
         * Configures the constraints with reasonable default values based on the
         * capabilities of the current device the VM is running on.
         *
         * \param physical_memory The total amount of physical memory on the current
         *   device, in bytes.
         * \param virtual_memory_limit The amount of virtual memory on the current
         *   device, in bytes, or zero, if there is no limit.
         */
        void ConfigureDefaults(uint64_t physical_memory,
                               uint64_t virtual_memory_limit);

        int max_semi_space_size() const {
            return max_semi_space_size_;
        }
        void set_max_semi_space_size(int limit_in_mb) {
            max_semi_space_size_ = limit_in_mb;
        }
        int max_old_space_size() const {
            return max_old_space_size_;
        }
        void set_max_old_space_size(int limit_in_mb) {
            max_old_space_size_ = limit_in_mb;
        }
        int max_executable_size() const {
            return max_executable_size_;
        }
        void set_max_executable_size(int limit_in_mb) {
            max_executable_size_ = limit_in_mb;
        }
        uint32_t* stack_limit() const {
            return stack_limit_;
        }
        // Sets an address beyond which the VM's stack may not grow.
        void set_stack_limit(uint32_t* value) {
            stack_limit_ = value;
        }
        size_t code_range_size() const {
            return code_range_size_;
        }
        void set_code_range_size(size_t limit_in_mb) {
            code_range_size_ = limit_in_mb;
        }

    private:
        int max_semi_space_size_;
        int max_old_space_size_;
        int max_executable_size_;
        uint32_t* stack_limit_;
        size_t code_range_size_;
};


// --- Exceptions ---


typedef void (*FatalErrorCallback)(const char* location, const char* message);

typedef void (*OOMErrorCallback)(const char* location, bool is_heap_oom);

typedef void (*MessageCallback)(Local<Message> message, Local<Value> error);

// --- Tracing ---

typedef void (*LogEventCallback)(const char* name, int event);

/**
 * Create new error objects by calling the corresponding error object
 * constructor with the message.
 */
class V8_EXPORT Exception {
    public:
        static Local<Value> RangeError(Local<String> message);
        static Local<Value> ReferenceError(Local<String> message);
        static Local<Value> SyntaxError(Local<String> message);
        static Local<Value> TypeError(Local<String> message);
        static Local<Value> Error(Local<String> message);

        /**
         * Creates an error message for the given exception.
         * Will try to reconstruct the original stack trace from the exception value,
         * or capture the current stack trace if not available.
         */
        static Local<Message> CreateMessage(Isolate* isolate, Local<Value> exception);
        V8_DEPRECATED("Use version with an Isolate*",
                      static Local<Message> CreateMessage(Local<Value> exception));

        /**
         * Returns the original stack trace that was captured at the creation time
         * of a given exception, or an empty handle if not available.
         */
        static Local<StackTrace> GetStackTrace(Local<Value> exception);
};


// --- Counters Callbacks ---

typedef int* (*CounterLookupCallback)(const char* name);

typedef void* (*CreateHistogramCallback)(const char* name,
        int min,
        int max,
        size_t buckets);

typedef void (*AddHistogramSampleCallback)(void* histogram, int sample);

// --- Memory Allocation Callback ---
enum ObjectSpace {
    kObjectSpaceNewSpace = 1 << 0,
    kObjectSpaceOldSpace = 1 << 1,
    kObjectSpaceCodeSpace = 1 << 2,
    kObjectSpaceMapSpace = 1 << 3,
    kObjectSpaceLoSpace = 1 << 4,
    kObjectSpaceAll = kObjectSpaceNewSpace | kObjectSpaceOldSpace |
                      kObjectSpaceCodeSpace | kObjectSpaceMapSpace |
                      kObjectSpaceLoSpace
};

enum AllocationAction {
    kAllocationActionAllocate = 1 << 0,
    kAllocationActionFree = 1 << 1,
    kAllocationActionAll = kAllocationActionAllocate | kAllocationActionFree
};

// --- Enter/Leave Script Callback ---
typedef void (*BeforeCallEnteredCallback)(Isolate*);
typedef void (*CallCompletedCallback)(Isolate*);
typedef void (*DeprecatedCallCompletedCallback)();

// --- Promise Reject Callback ---
enum PromiseRejectEvent {
    kPromiseRejectWithNoHandler = 0,
    kPromiseHandlerAddedAfterReject = 1
};

class PromiseRejectMessage {
    public:
        PromiseRejectMessage(Local<Promise> promise, PromiseRejectEvent event,
                             Local<Value> value, Local<StackTrace> stack_trace)
            : promise_(promise),
              event_(event),
              value_(value),
              stack_trace_(stack_trace) {}

        V8_INLINE Local<Promise> GetPromise() const {
            return promise_;
        }
        V8_INLINE PromiseRejectEvent GetEvent() const {
            return event_;
        }
        V8_INLINE Local<Value> GetValue() const {
            return value_;
        }

        V8_DEPRECATED("Use v8::Exception::CreateMessage(GetValue())->GetStackTrace()",
                      V8_INLINE Local<StackTrace> GetStackTrace() const) {
            return stack_trace_;
        }

    private:
        Local<Promise> promise_;
        PromiseRejectEvent event_;
        Local<Value> value_;
        Local<StackTrace> stack_trace_;
};

typedef void (*PromiseRejectCallback)(PromiseRejectMessage message);

// --- Microtasks Callbacks ---
typedef void (*MicrotasksCompletedCallback)(Isolate*);
typedef void (*MicrotaskCallback)(void* data);


/**
 * Policy for running microtasks:
 *   - explicit: microtasks are invoked with Isolate::RunMicrotasks() method;
 *   - scoped: microtasks invocation is controlled by MicrotasksScope objects;
 *   - auto: microtasks are invoked when the script call depth decrements
 *           to zero.
 */
enum class MicrotasksPolicy { kExplicit, kScoped, kAuto };


/**
 * This scope is used to control microtasks when kScopeMicrotasksInvocation
 * is used on Isolate. In this mode every non-primitive call to V8 should be
 * done inside some MicrotasksScope.
 * Microtasks are executed when topmost MicrotasksScope marked as kRunMicrotasks
 * exits.
 * kDoNotRunMicrotasks should be used to annotate calls not intended to trigger
 * microtasks.
 */
class V8_EXPORT MicrotasksScope {
    public:
        enum Type { kRunMicrotasks, kDoNotRunMicrotasks };

        MicrotasksScope(Isolate* isolate, Type type);
        ~MicrotasksScope();

        /**
         * Runs microtasks if no kRunMicrotasks scope is currently active.
         */
        static void PerformCheckpoint(Isolate* isolate);

        /**
         * Returns current depth of nested kRunMicrotasks scopes.
         */
        static int GetCurrentDepth(Isolate* isolate);

        /**
         * Returns true while microtasks are being executed.
         */
        static bool IsRunningMicrotasks(Isolate* isolate);

        // Prevent copying.
        MicrotasksScope(const MicrotasksScope&) = delete;
        MicrotasksScope& operator=(const MicrotasksScope&) = delete;

    private:
        internal::Isolate* const isolate_;
        bool run_;
};


// --- Failed Access Check Callback ---
typedef void (*FailedAccessCheckCallback)(Local<Object> target,
        AccessType type,
        Local<Value> data);

// --- AllowCodeGenerationFromStrings callbacks ---

/**
 * Callback to check if code generation from strings is allowed. See
 * Context::AllowCodeGenerationFromStrings.
 */
typedef bool (*AllowCodeGenerationFromStringsCallback)(Local<Context> context);

// --- Garbage Collection Callbacks ---

/**
 * Applications can register callback functions which will be called before and
 * after certain garbage collection operations.  Allocations are not allowed in
 * the callback functions, you therefore cannot manipulate objects (set or
 * delete properties for example) since it is possible such operations will
 * result in the allocation of objects.
 */
enum GCType {
    kGCTypeScavenge = 1 << 0,
    kGCTypeMarkSweepCompact = 1 << 1,
    kGCTypeIncrementalMarking = 1 << 2,
    kGCTypeProcessWeakCallbacks = 1 << 3,
    kGCTypeAll = kGCTypeScavenge | kGCTypeMarkSweepCompact |
                 kGCTypeIncrementalMarking | kGCTypeProcessWeakCallbacks
};

/**
 * GCCallbackFlags is used to notify additional information about the GC
 * callback.
 *   - kGCCallbackFlagConstructRetainedObjectInfos: The GC callback is for
 *     constructing retained object infos.
 *   - kGCCallbackFlagForced: The GC callback is for a forced GC for testing.
 *   - kGCCallbackFlagSynchronousPhantomCallbackProcessing: The GC callback
 *     is called synchronously without getting posted to an idle task.
 *   - kGCCallbackFlagCollectAllAvailableGarbage: The GC callback is called
 *     in a phase where V8 is trying to collect all available garbage
 *     (e.g., handling a low memory notification).
 */
enum GCCallbackFlags {
    kNoGCCallbackFlags = 0,
    kGCCallbackFlagConstructRetainedObjectInfos = 1 << 1,
    kGCCallbackFlagForced = 1 << 2,
    kGCCallbackFlagSynchronousPhantomCallbackProcessing = 1 << 3,
    kGCCallbackFlagCollectAllAvailableGarbage = 1 << 4,
    kGCCallbackFlagCollectAllExternalMemory = 1 << 5,
};

typedef void (*GCCallback)(GCType type, GCCallbackFlags flags);

typedef void (*InterruptCallback)(Isolate* isolate, void* data);


/**
 * Collection of V8 heap information.
 *
 * Instances of this class can be passed to v8::V8::HeapStatistics to
 * get heap statistics from V8.
 */
class V8_EXPORT HeapStatistics {
    public:
        HeapStatistics();
        size_t total_heap_size() {
            return total_heap_size_;
        }
        size_t total_heap_size_executable() {
            return total_heap_size_executable_;
        }
        size_t total_physical_size() {
            return total_physical_size_;
        }
        size_t total_available_size() {
            return total_available_size_;
        }
        size_t used_heap_size() {
            return used_heap_size_;
        }
        size_t heap_size_limit() {
            return heap_size_limit_;
        }
        size_t malloced_memory() {
            return malloced_memory_;
        }
        size_t peak_malloced_memory() {
            return peak_malloced_memory_;
        }
        size_t does_zap_garbage() {
            return does_zap_garbage_;
        }

    private:
        size_t total_heap_size_;
        size_t total_heap_size_executable_;
        size_t total_physical_size_;
        size_t total_available_size_;
        size_t used_heap_size_;
        size_t heap_size_limit_;
        size_t malloced_memory_;
        size_t peak_malloced_memory_;
        bool does_zap_garbage_;

        friend class V8;
        friend class Isolate;
};


class V8_EXPORT HeapSpaceStatistics {
    public:
        HeapSpaceStatistics();
        const char* space_name() {
            return space_name_;
        }
        size_t space_size() {
            return space_size_;
        }
        size_t space_used_size() {
            return space_used_size_;
        }
        size_t space_available_size() {
            return space_available_size_;
        }
        size_t physical_space_size() {
            return physical_space_size_;
        }

    private:
        const char* space_name_;
        size_t space_size_;
        size_t space_used_size_;
        size_t space_available_size_;
        size_t physical_space_size_;

        friend class Isolate;
};


class V8_EXPORT HeapObjectStatistics {
    public:
        HeapObjectStatistics();
        const char* object_type() {
            return object_type_;
        }
        const char* object_sub_type() {
            return object_sub_type_;
        }
        size_t object_count() {
            return object_count_;
        }
        size_t object_size() {
            return object_size_;
        }

    private:
        const char* object_type_;
        const char* object_sub_type_;
        size_t object_count_;
        size_t object_size_;

        friend class Isolate;
};

class V8_EXPORT HeapCodeStatistics {
    public:
        HeapCodeStatistics();
        size_t code_and_metadata_size() {
            return code_and_metadata_size_;
        }
        size_t bytecode_and_metadata_size() {
            return bytecode_and_metadata_size_;
        }

    private:
        size_t code_and_metadata_size_;
        size_t bytecode_and_metadata_size_;

        friend class Isolate;
};

class RetainedObjectInfo;


/**
 * FunctionEntryHook is the type of the profile entry hook called at entry to
 * any generated function when function-level profiling is enabled.
 *
 * \param function the address of the function that's being entered.
 * \param return_addr_location points to a location on stack where the machine
 *    return address resides. This can be used to identify the caller of
 *    \p function, and/or modified to divert execution when \p function exits.
 *
 * \note the entry hook must not cause garbage collection.
 */
typedef void (*FunctionEntryHook)(uintptr_t function,
                                  uintptr_t return_addr_location);

/**
 * A JIT code event is issued each time code is added, moved or removed.
 *
 * \note removal events are not currently issued.
 */
struct JitCodeEvent {
    enum EventType {
        CODE_ADDED,
        CODE_MOVED,
        CODE_REMOVED,
        CODE_ADD_LINE_POS_INFO,
        CODE_START_LINE_INFO_RECORDING,
        CODE_END_LINE_INFO_RECORDING
    };
    // Definition of the code position type. The "POSITION" type means the place
    // in the source code which are of interest when making stack traces to
    // pin-point the source location of a stack frame as close as possible.
    // The "STATEMENT_POSITION" means the place at the beginning of each
    // statement, and is used to indicate possible break locations.
    enum PositionType { POSITION, STATEMENT_POSITION };

    // Type of event.
    EventType type;
    // Start of the instructions.
    void* code_start;
    // Size of the instructions.
    size_t code_len;
    // Script info for CODE_ADDED event.
    Local<UnboundScript> script;
    // User-defined data for *_LINE_INFO_* event. It's used to hold the source
    // code line information which is returned from the
    // CODE_START_LINE_INFO_RECORDING event. And it's passed to subsequent
    // CODE_ADD_LINE_POS_INFO and CODE_END_LINE_INFO_RECORDING events.
    void* user_data;

    struct name_t {
        // Name of the object associated with the code, note that the string is not
        // zero-terminated.
        const char* str;
        // Number of chars in str.
        size_t len;
    };

    struct line_info_t {
        // PC offset
        size_t offset;
        // Code postion
        size_t pos;
        // The position type.
        PositionType position_type;
    };

    union {
        // Only valid for CODE_ADDED.
        struct name_t name;

        // Only valid for CODE_ADD_LINE_POS_INFO
        struct line_info_t line_info;

        // New location of instructions. Only valid for CODE_MOVED.
        void* new_code_start;
    };
};

/**
 * Option flags passed to the SetRAILMode function.
 * See documentation https://developers.google.com/web/tools/chrome-devtools/
 * profile/evaluate-performance/rail
 */
enum RAILMode {
    // Response performance mode: In this mode very low virtual machine latency
    // is provided. V8 will try to avoid JavaScript execution interruptions.
    // Throughput may be throttled.
    PERFORMANCE_RESPONSE,
    // Animation performance mode: In this mode low virtual machine latency is
    // provided. V8 will try to avoid as many JavaScript execution interruptions
    // as possible. Throughput may be throttled. This is the default mode.
    PERFORMANCE_ANIMATION,
    // Idle performance mode: The embedder is idle. V8 can complete deferred work
    // in this mode.
    PERFORMANCE_IDLE,
    // Load performance mode: In this mode high throughput is provided. V8 may
    // turn off latency optimizations.
    PERFORMANCE_LOAD
};

/**
 * Option flags passed to the SetJitCodeEventHandler function.
 */
enum JitCodeEventOptions {
    kJitCodeEventDefault = 0,
    // Generate callbacks for already existent code.
    kJitCodeEventEnumExisting = 1
};


/**
 * Callback function passed to SetJitCodeEventHandler.
 *
 * \param event code add, move or removal event.
 */
typedef void (*JitCodeEventHandler)(const JitCodeEvent* event);


/**
 * Interface for iterating through all external resources in the heap.
 */
class V8_EXPORT ExternalResourceVisitor {  // NOLINT
    public:
        virtual ~ExternalResourceVisitor() {}
        virtual void VisitExternalString(Local<String> string) {}
};


/**
 * Interface for iterating through all the persistent handles in the heap.
 */
class V8_EXPORT PersistentHandleVisitor {  // NOLINT
    public:
        virtual ~PersistentHandleVisitor() {}
        virtual void VisitPersistentHandle(Persistent<Value>* value,
                                           uint16_t class_id) {}
};

/**
 * Memory pressure level for the MemoryPressureNotification.
 * kNone hints V8 that there is no memory pressure.
 * kModerate hints V8 to speed up incremental garbage collection at the cost of
 * of higher latency due to garbage collection pauses.
 * kCritical hints V8 to free memory as soon as possible. Garbage collection
 * pauses at this level will be large.
 */
enum class MemoryPressureLevel { kNone, kModerate, kCritical };

/**
 * Interface for tracing through the embedder heap. During the v8 garbage
 * collection, v8 collects hidden fields of all potential wrappers, and at the
 * end of its marking phase iterates the collection and asks the embedder to
 * trace through its heap and use reporter to report each js object reachable
 * from any of the given wrappers.
 *
 * Before the first call to the TraceWrappersFrom function TracePrologue will be
 * called. When the garbage collection cycle is finished, TraceEpilogue will be
 * called.
 */
class V8_EXPORT EmbedderHeapTracer {
    public:
        enum ForceCompletionAction { FORCE_COMPLETION, DO_NOT_FORCE_COMPLETION };

        struct AdvanceTracingActions {
            explicit AdvanceTracingActions(ForceCompletionAction force_completion_)
                : force_completion(force_completion_) {}

            ForceCompletionAction force_completion;
        };

        /**
         * V8 will call this method with internal fields of found wrappers. The
         * embedder is expected to store them in its marking deque and trace
         * reachable wrappers from them when called through |AdvanceTracing|.
         */
        virtual void RegisterV8References(
            const std::vector<std::pair<void*, void*> >& internal_fields) = 0;

        /**
         * Deprecated.
         * TODO(hlopko) Remove once the migration to reporter is finished.
         */
        virtual void TracePrologue() {}

        /**
         * V8 will call this method at the beginning of a GC cycle. Embedder is
         * expected to use EmbedderReachableReferenceReporter for reporting all
         * reachable v8 objects.
         */
        virtual void TracePrologue(EmbedderReachableReferenceReporter* reporter) {}

        /**
         * Embedder is expected to trace its heap starting from wrappers reported by
         * RegisterV8References method, and use reporter for all reachable wrappers.
         * Embedder is expected to stop tracing by the given deadline.
         *
         * Returns true if there is still work to do.
         */
        virtual bool AdvanceTracing(double deadline_in_ms,
                                    AdvanceTracingActions actions) = 0;

        /**
         * V8 will call this method at the end of a GC cycle.
         *
         * Note that allocation is *not* allowed within |TraceEpilogue|.
         */
        virtual void TraceEpilogue() = 0;

        /**
         * Let embedder know v8 entered final marking pause (no more incremental steps
         * will follow).
         */
        virtual void EnterFinalPause() {}

        /**
         * Throw away all intermediate data and reset to the initial state.
         */
        virtual void AbortTracing() {}

        /**
         * Returns the number of wrappers that are still to be traced by the embedder.
         */
        virtual size_t NumberOfWrappersToTrace() {
            return 0;
        }

    protected:
        virtual ~EmbedderHeapTracer() = default;
};

/**
 * Isolate represents an isolated instance of the V8 engine.  V8 isolates have
 * completely separate states.  Objects from one isolate must not be used in
 * other isolates.  The embedder can create multiple isolates and use them in
 * parallel in multiple threads.  An isolate can be entered by at most one
 * thread at any given time.  The Locker/Unlocker API must be used to
 * synchronize.
 */
class V8_EXPORT Isolate {
    public:
        /**
         * Initial configuration parameters for a new Isolate.
         */
        struct CreateParams {
            CreateParams()
                : entry_hook(nullptr),
                  code_event_handler(nullptr),
                  snapshot_blob(nullptr),
                  counter_lookup_callback(nullptr),
                  create_histogram_callback(nullptr),
                  add_histogram_sample_callback(nullptr),
                  array_buffer_allocator(nullptr),
                  external_references(nullptr) {}

            /**
             * The optional entry_hook allows the host application to provide the
             * address of a function that's invoked on entry to every V8-generated
             * function.  Note that entry_hook is invoked at the very start of each
             * generated function. Furthermore, if an entry_hook is given, V8 will
             * not use a snapshot, including custom snapshots.
             */
            FunctionEntryHook entry_hook;

            /**
             * Allows the host application to provide the address of a function that is
             * notified each time code is added, moved or removed.
             */
            JitCodeEventHandler code_event_handler;

            /**
             * ResourceConstraints to use for the new Isolate.
             */
            ResourceConstraints constraints;

            /**
             * Explicitly specify a startup snapshot blob. The embedder owns the blob.
             */
            StartupData* snapshot_blob;


            /**
             * Enables the host application to provide a mechanism for recording
             * statistics counters.
             */
            CounterLookupCallback counter_lookup_callback;

            /**
             * Enables the host application to provide a mechanism for recording
             * histograms. The CreateHistogram function returns a
             * histogram which will later be passed to the AddHistogramSample
             * function.
             */
            CreateHistogramCallback create_histogram_callback;
            AddHistogramSampleCallback add_histogram_sample_callback;

            /**
             * The ArrayBuffer::Allocator to use for allocating and freeing the backing
             * store of ArrayBuffers.
             */
            ArrayBuffer::Allocator* array_buffer_allocator;

            /**
             * Specifies an optional nullptr-terminated array of raw addresses in the
             * embedder that V8 can match against during serialization and use for
             * deserialization. This array and its content must stay valid for the
             * entire lifetime of the isolate.
             */
            intptr_t* external_references;
        };


        /**
         * Stack-allocated class which sets the isolate for all operations
         * executed within a local scope.
         */
        class V8_EXPORT Scope {
            public:
                explicit Scope(Isolate* isolate) : isolate_(isolate) {
                    isolate->Enter();
                }

                ~Scope() {
                    isolate_->Exit();
                }

                // Prevent copying of Scope objects.
                Scope(const Scope&) = delete;
                Scope& operator=(const Scope&) = delete;

            private:
                Isolate* const isolate_;
        };


        /**
         * Assert that no Javascript code is invoked.
         */
        class V8_EXPORT DisallowJavascriptExecutionScope {
            public:
                enum OnFailure { CRASH_ON_FAILURE, THROW_ON_FAILURE };

                DisallowJavascriptExecutionScope(Isolate* isolate, OnFailure on_failure);
                ~DisallowJavascriptExecutionScope();

                // Prevent copying of Scope objects.
                DisallowJavascriptExecutionScope(const DisallowJavascriptExecutionScope&) =
                    delete;
                DisallowJavascriptExecutionScope& operator=(
                    const DisallowJavascriptExecutionScope&) = delete;

            private:
                bool on_failure_;
                void* internal_;
        };


        /**
         * Introduce exception to DisallowJavascriptExecutionScope.
         */
        class V8_EXPORT AllowJavascriptExecutionScope {
            public:
                explicit AllowJavascriptExecutionScope(Isolate* isolate);
                ~AllowJavascriptExecutionScope();

                // Prevent copying of Scope objects.
                AllowJavascriptExecutionScope(const AllowJavascriptExecutionScope&) =
                    delete;
                AllowJavascriptExecutionScope& operator=(
                    const AllowJavascriptExecutionScope&) = delete;

            private:
                void* internal_throws_;
                void* internal_assert_;
        };

        /**
         * Do not run microtasks while this scope is active, even if microtasks are
         * automatically executed otherwise.
         */
        class V8_EXPORT SuppressMicrotaskExecutionScope {
            public:
                explicit SuppressMicrotaskExecutionScope(Isolate* isolate);
                ~SuppressMicrotaskExecutionScope();

                // Prevent copying of Scope objects.
                SuppressMicrotaskExecutionScope(const SuppressMicrotaskExecutionScope&) =
                    delete;
                SuppressMicrotaskExecutionScope& operator=(
                    const SuppressMicrotaskExecutionScope&) = delete;

            private:
                internal::Isolate* const isolate_;
        };

        /**
         * Types of garbage collections that can be requested via
         * RequestGarbageCollectionForTesting.
         */
        enum GarbageCollectionType {
            kFullGarbageCollection,
            kMinorGarbageCollection
        };

        /**
         * Features reported via the SetUseCounterCallback callback. Do not change
         * assigned numbers of existing items; add new features to the end of this
         * list.
         */
        enum UseCounterFeature {
            kUseAsm = 0,
            kBreakIterator = 1,
            kLegacyConst = 2,
            kMarkDequeOverflow = 3,
            kStoreBufferOverflow = 4,
            kSlotsBufferOverflow = 5,
            kObjectObserve = 6,
            kForcedGC = 7,
            kSloppyMode = 8,
            kStrictMode = 9,
            kStrongMode = 10,
            kRegExpPrototypeStickyGetter = 11,
            kRegExpPrototypeToString = 12,
            kRegExpPrototypeUnicodeGetter = 13,
            kIntlV8Parse = 14,
            kIntlPattern = 15,
            kIntlResolved = 16,
            kPromiseChain = 17,
            kPromiseAccept = 18,
            kPromiseDefer = 19,
            kHtmlCommentInExternalScript = 20,
            kHtmlComment = 21,
            kSloppyModeBlockScopedFunctionRedefinition = 22,
            kForInInitializer = 23,
            kArrayProtectorDirtied = 24,
            kArraySpeciesModified = 25,
            kArrayPrototypeConstructorModified = 26,
            kArrayInstanceProtoModified = 27,
            kArrayInstanceConstructorModified = 28,
            kLegacyFunctionDeclaration = 29,
            kRegExpPrototypeSourceGetter = 30,
            kRegExpPrototypeOldFlagGetter = 31,
            kDecimalWithLeadingZeroInStrictMode = 32,
            kLegacyDateParser = 33,
            kDefineGetterOrSetterWouldThrow = 34,
            kFunctionConstructorReturnedUndefined = 35,

            // If you add new values here, you'll also need to update Chromium's:
            // UseCounter.h, V8PerIsolateData.cpp, histograms.xml
            kUseCounterFeatureCount  // This enum value must be last.
        };

        typedef void (*UseCounterCallback)(Isolate* isolate,
                                           UseCounterFeature feature);


        /**
         * Creates a new isolate.  Does not change the currently entered
         * isolate.
         *
         * When an isolate is no longer used its resources should be freed
         * by calling Dispose().  Using the delete operator is not allowed.
         *
         * V8::Initialize() must have run prior to this.
         */
        static Isolate* New(const CreateParams& params);

        /**
         * Returns the entered isolate for the current thread or NULL in
         * case there is no current isolate.
         *
         * This method must not be invoked before V8::Initialize() was invoked.
         */
        static Isolate* GetCurrent();

        /**
         * Custom callback used by embedders to help V8 determine if it should abort
         * when it throws and no internal handler is predicted to catch the
         * exception. If --abort-on-uncaught-exception is used on the command line,
         * then V8 will abort if either:
         * - no custom callback is set.
         * - the custom callback set returns true.
         * Otherwise, the custom callback will not be called and V8 will not abort.
         */
        typedef bool (*AbortOnUncaughtExceptionCallback)(Isolate*);
        void SetAbortOnUncaughtExceptionCallback(
            AbortOnUncaughtExceptionCallback callback);

        /**
         * Optional notification that the system is running low on memory.
         * V8 uses these notifications to guide heuristics.
         * It is allowed to call this function from another thread while
         * the isolate is executing long running JavaScript code.
         */
        void MemoryPressureNotification(MemoryPressureLevel level);

        /**
         * Methods below this point require holding a lock (using Locker) in
         * a multi-threaded environment.
         */

        /**
         * Sets this isolate as the entered one for the current thread.
         * Saves the previously entered one (if any), so that it can be
         * restored when exiting.  Re-entering an isolate is allowed.
         */
        void Enter();

        /**
         * Exits this isolate by restoring the previously entered one in the
         * current thread.  The isolate may still stay the same, if it was
         * entered more than once.
         *
         * Requires: this == Isolate::GetCurrent().
         */
        void Exit();

        /**
         * Disposes the isolate.  The isolate must not be entered by any
         * thread to be disposable.
         */
        void Dispose();

        /**
         * Discards all V8 thread-specific data for the Isolate. Should be used
         * if a thread is terminating and it has used an Isolate that will outlive
         * the thread -- all thread-specific data for an Isolate is discarded when
         * an Isolate is disposed so this call is pointless if an Isolate is about
         * to be Disposed.
         */
        void DiscardThreadSpecificMetadata();

        /**
         * Associate embedder-specific data with the isolate. |slot| has to be
         * between 0 and GetNumberOfDataSlots() - 1.
         */
        V8_INLINE void SetData(uint32_t slot, void* data);

        /**
         * Retrieve embedder-specific data from the isolate.
         * Returns NULL if SetData has never been called for the given |slot|.
         */
        V8_INLINE void* GetData(uint32_t slot);

        /**
         * Returns the maximum number of available embedder data slots. Valid slots
         * are in the range of 0 - GetNumberOfDataSlots() - 1.
         */
        V8_INLINE static uint32_t GetNumberOfDataSlots();

        /**
         * Get statistics about the heap memory usage.
         */
        void GetHeapStatistics(HeapStatistics* heap_statistics);

        /**
         * Returns the number of spaces in the heap.
         */
        size_t NumberOfHeapSpaces();

        /**
         * Get the memory usage of a space in the heap.
         *
         * \param space_statistics The HeapSpaceStatistics object to fill in
         *   statistics.
         * \param index The index of the space to get statistics from, which ranges
         *   from 0 to NumberOfHeapSpaces() - 1.
         * \returns true on success.
         */
        bool GetHeapSpaceStatistics(HeapSpaceStatistics* space_statistics,
                                    size_t index);

        /**
         * Returns the number of types of objects tracked in the heap at GC.
         */
        size_t NumberOfTrackedHeapObjectTypes();

        /**
         * Get statistics about objects in the heap.
         *
         * \param object_statistics The HeapObjectStatistics object to fill in
         *   statistics of objects of given type, which were live in the previous GC.
         * \param type_index The index of the type of object to fill details about,
         *   which ranges from 0 to NumberOfTrackedHeapObjectTypes() - 1.
         * \returns true on success.
         */
        bool GetHeapObjectStatisticsAtLastGC(HeapObjectStatistics* object_statistics,
                                             size_t type_index);

        /**
         * Get statistics about code and its metadata in the heap.
         *
         * \param object_statistics The HeapCodeStatistics object to fill in
         *   statistics of code, bytecode and their metadata.
         * \returns true on success.
         */
        bool GetHeapCodeAndMetadataStatistics(HeapCodeStatistics* object_statistics);

        /**
         * Get a call stack sample from the isolate.
         * \param state Execution state.
         * \param frames Caller allocated buffer to store stack frames.
         * \param frames_limit Maximum number of frames to capture. The buffer must
         *                     be large enough to hold the number of frames.
         * \param sample_info The sample info is filled up by the function
         *                    provides number of actual captured stack frames and
         *                    the current VM state.
         * \note GetStackSample should only be called when the JS thread is paused or
         *       interrupted. Otherwise the behavior is undefined.
         */
        void GetStackSample(const RegisterState& state, void** frames,
                            size_t frames_limit, SampleInfo* sample_info);

        /**
         * Adjusts the amount of registered external memory. Used to give V8 an
         * indication of the amount of externally allocated memory that is kept alive
         * by JavaScript objects. V8 uses this to decide when to perform global
         * garbage collections. Registering externally allocated memory will trigger
         * global garbage collections more often than it would otherwise in an attempt
         * to garbage collect the JavaScript objects that keep the externally
         * allocated memory alive.
         *
         * \param change_in_bytes the change in externally allocated memory that is
         *   kept alive by JavaScript objects.
         * \returns the adjusted value.
         */
        V8_INLINE int64_t
        AdjustAmountOfExternalAllocatedMemory(int64_t change_in_bytes);

        /**
         * Returns the number of phantom handles without callbacks that were reset
         * by the garbage collector since the last call to this function.
         */
        size_t NumberOfPhantomHandleResetsSinceLastCall();

        /**
         * Returns heap profiler for this isolate. Will return NULL until the isolate
         * is initialized.
         */
        HeapProfiler* GetHeapProfiler();

        /**
         * Returns CPU profiler for this isolate. Will return NULL unless the isolate
         * is initialized. It is the embedder's responsibility to stop all CPU
         * profiling activities if it has started any.
         */
        V8_DEPRECATE_SOON("CpuProfiler should be created with CpuProfiler::New call.",
                          CpuProfiler* GetCpuProfiler());

        /** Returns true if this isolate has a current context. */
        bool InContext();

        /**
         * Returns the context of the currently running JavaScript, or the context
         * on the top of the stack if no JavaScript is running.
         */
        Local<Context> GetCurrentContext();

        /**
         * Returns the context of the calling JavaScript code.  That is the
         * context of the top-most JavaScript frame.  If there are no
         * JavaScript frames an empty handle is returned.
         */
        V8_DEPRECATE_SOON(
            "Calling context concept is not compatible with tail calls, and will be "
            "removed.",
            Local<Context> GetCallingContext());

        /** Returns the last context entered through V8's C++ API. */
        Local<Context> GetEnteredContext();

        /**
         * Schedules an exception to be thrown when returning to JavaScript.  When an
         * exception has been scheduled it is illegal to invoke any JavaScript
         * operation; the caller must return immediately and only after the exception
         * has been handled does it become legal to invoke JavaScript operations.
         */
        Local<Value> ThrowException(Local<Value> exception);

        /**
         * Allows the host application to group objects together. If one
         * object in the group is alive, all objects in the group are alive.
         * After each garbage collection, object groups are removed. It is
         * intended to be used in the before-garbage-collection callback
         * function, for instance to simulate DOM tree connections among JS
         * wrapper objects. Object groups for all dependent handles need to
         * be provided for kGCTypeMarkSweepCompact collections, for all other
         * garbage collection types it is sufficient to provide object groups
         * for partially dependent handles only.
         */
        template<typename T> void SetObjectGroupId(const Persistent<T>& object,
                UniqueId id);

        /**
         * Allows the host application to declare implicit references from an object
         * group to an object. If the objects of the object group are alive, the child
         * object is alive too. After each garbage collection, all implicit references
         * are removed. It is intended to be used in the before-garbage-collection
         * callback function.
         */
        template<typename T> void SetReferenceFromGroup(UniqueId id,
                const Persistent<T>& child);

        /**
         * Allows the host application to declare implicit references from an object
         * to another object. If the parent object is alive, the child object is alive
         * too. After each garbage collection, all implicit references are removed. It
         * is intended to be used in the before-garbage-collection callback function.
         */
        template<typename T, typename S>
        void SetReference(const Persistent<T>& parent, const Persistent<S>& child);

        typedef void (*GCCallback)(Isolate* isolate, GCType type,
                                   GCCallbackFlags flags);

        /**
         * Enables the host application to receive a notification before a
         * garbage collection. Allocations are allowed in the callback function,
         * but the callback is not re-entrant: if the allocation inside it will
         * trigger the garbage collection, the callback won't be called again.
         * It is possible to specify the GCType filter for your callback. But it is
         * not possible to register the same callback function two times with
         * different GCType filters.
         */
        void AddGCPrologueCallback(GCCallback callback,
                                   GCType gc_type_filter = kGCTypeAll);

        /**
         * This function removes callback which was installed by
         * AddGCPrologueCallback function.
         */
        void RemoveGCPrologueCallback(GCCallback callback);

        /**
         * Sets the embedder heap tracer for the isolate.
         */
        void SetEmbedderHeapTracer(EmbedderHeapTracer* tracer);

        /**
         * Enables the host application to receive a notification after a
         * garbage collection. Allocations are allowed in the callback function,
         * but the callback is not re-entrant: if the allocation inside it will
         * trigger the garbage collection, the callback won't be called again.
         * It is possible to specify the GCType filter for your callback. But it is
         * not possible to register the same callback function two times with
         * different GCType filters.
         */
        void AddGCEpilogueCallback(GCCallback callback,
                                   GCType gc_type_filter = kGCTypeAll);

        /**
         * This function removes callback which was installed by
         * AddGCEpilogueCallback function.
         */
        void RemoveGCEpilogueCallback(GCCallback callback);

        /**
         * Forcefully terminate the current thread of JavaScript execution
         * in the given isolate.
         *
         * This method can be used by any thread even if that thread has not
         * acquired the V8 lock with a Locker object.
         */
        void TerminateExecution();

        /**
         * Is V8 terminating JavaScript execution.
         *
         * Returns true if JavaScript execution is currently terminating
         * because of a call to TerminateExecution.  In that case there are
         * still JavaScript frames on the stack and the termination
         * exception is still active.
         */
        bool IsExecutionTerminating();

        /**
         * Resume execution capability in the given isolate, whose execution
         * was previously forcefully terminated using TerminateExecution().
         *
         * When execution is forcefully terminated using TerminateExecution(),
         * the isolate can not resume execution until all JavaScript frames
         * have propagated the uncatchable exception which is generated.  This
         * method allows the program embedding the engine to handle the
         * termination event and resume execution capability, even if
         * JavaScript frames remain on the stack.
         *
         * This method can be used by any thread even if that thread has not
         * acquired the V8 lock with a Locker object.
         */
        void CancelTerminateExecution();

        /**
         * Request V8 to interrupt long running JavaScript code and invoke
         * the given |callback| passing the given |data| to it. After |callback|
         * returns control will be returned to the JavaScript code.
         * There may be a number of interrupt requests in flight.
         * Can be called from another thread without acquiring a |Locker|.
         * Registered |callback| must not reenter interrupted Isolate.
         */
        void RequestInterrupt(InterruptCallback callback, void* data);

        /**
         * Request garbage collection in this Isolate. It is only valid to call this
         * function if --expose_gc was specified.
         *
         * This should only be used for testing purposes and not to enforce a garbage
         * collection schedule. It has strong negative impact on the garbage
         * collection performance. Use IdleNotificationDeadline() or
         * LowMemoryNotification() instead to influence the garbage collection
         * schedule.
         */
        void RequestGarbageCollectionForTesting(GarbageCollectionType type);

        /**
         * Set the callback to invoke for logging event.
         */
        void SetEventLogger(LogEventCallback that);

        /**
         * Adds a callback to notify the host application right before a script
         * is about to run. If a script re-enters the runtime during executing, the
         * BeforeCallEnteredCallback is invoked for each re-entrance.
         * Executing scripts inside the callback will re-trigger the callback.
         */
        void AddBeforeCallEnteredCallback(BeforeCallEnteredCallback callback);

        /**
         * Removes callback that was installed by AddBeforeCallEnteredCallback.
         */
        void RemoveBeforeCallEnteredCallback(BeforeCallEnteredCallback callback);

        /**
         * Adds a callback to notify the host application when a script finished
         * running.  If a script re-enters the runtime during executing, the
         * CallCompletedCallback is only invoked when the outer-most script
         * execution ends.  Executing scripts inside the callback do not trigger
         * further callbacks.
         */
        void AddCallCompletedCallback(CallCompletedCallback callback);
        V8_DEPRECATE_SOON(
            "Use callback with parameter",
            void AddCallCompletedCallback(DeprecatedCallCompletedCallback callback));

        /**
         * Removes callback that was installed by AddCallCompletedCallback.
         */
        void RemoveCallCompletedCallback(CallCompletedCallback callback);
        V8_DEPRECATE_SOON(
            "Use callback with parameter",
            void RemoveCallCompletedCallback(
                DeprecatedCallCompletedCallback callback));

        /**
         * Set callback to notify about promise reject with no handler, or
         * revocation of such a previous notification once the handler is added.
         */
        void SetPromiseRejectCallback(PromiseRejectCallback callback);

        /**
         * Experimental: Runs the Microtask Work Queue until empty
         * Any exceptions thrown by microtask callbacks are swallowed.
         */
        void RunMicrotasks();

        /**
         * Experimental: Enqueues the callback to the Microtask Work Queue
         */
        void EnqueueMicrotask(Local<Function> microtask);

        /**
         * Experimental: Enqueues the callback to the Microtask Work Queue
         */
        void EnqueueMicrotask(MicrotaskCallback microtask, void* data = NULL);

        /**
         * Experimental: Controls how Microtasks are invoked. See MicrotasksPolicy
         * for details.
         */
        void SetMicrotasksPolicy(MicrotasksPolicy policy);
        V8_DEPRECATE_SOON("Use SetMicrotasksPolicy",
                          void SetAutorunMicrotasks(bool autorun));

        /**
         * Experimental: Returns the policy controlling how Microtasks are invoked.
         */
        MicrotasksPolicy GetMicrotasksPolicy() const;
        V8_DEPRECATE_SOON("Use GetMicrotasksPolicy",
                          bool WillAutorunMicrotasks() const);

        /**
         * Experimental: adds a callback to notify the host application after
         * microtasks were run. The callback is triggered by explicit RunMicrotasks
         * call or automatic microtasks execution (see SetAutorunMicrotasks).
         *
         * Callback will trigger even if microtasks were attempted to run,
         * but the microtasks queue was empty and no single microtask was actually
         * executed.
         *
         * Executing scriptsinside the callback will not re-trigger microtasks and
         * the callback.
         */
        void AddMicrotasksCompletedCallback(MicrotasksCompletedCallback callback);

        /**
         * Removes callback that was installed by AddMicrotasksCompletedCallback.
         */
        void RemoveMicrotasksCompletedCallback(MicrotasksCompletedCallback callback);

        /**
         * Sets a callback for counting the number of times a feature of V8 is used.
         */
        void SetUseCounterCallback(UseCounterCallback callback);

        /**
         * Enables the host application to provide a mechanism for recording
         * statistics counters.
         */
        void SetCounterFunction(CounterLookupCallback);

        /**
         * Enables the host application to provide a mechanism for recording
         * histograms. The CreateHistogram function returns a
         * histogram which will later be passed to the AddHistogramSample
         * function.
         */
        void SetCreateHistogramFunction(CreateHistogramCallback);
        void SetAddHistogramSampleFunction(AddHistogramSampleCallback);

        /**
         * Optional notification that the embedder is idle.
         * V8 uses the notification to perform garbage collection.
         * This call can be used repeatedly if the embedder remains idle.
         * Returns true if the embedder should stop calling IdleNotificationDeadline
         * until real work has been done.  This indicates that V8 has done
         * as much cleanup as it will be able to do.
         *
         * The deadline_in_seconds argument specifies the deadline V8 has to finish
         * garbage collection work. deadline_in_seconds is compared with
         * MonotonicallyIncreasingTime() and should be based on the same timebase as
         * that function. There is no guarantee that the actual work will be done
         * within the time limit.
         */
        bool IdleNotificationDeadline(double deadline_in_seconds);

        V8_DEPRECATED("use IdleNotificationDeadline()",
                      bool IdleNotification(int idle_time_in_ms));

        /**
         * Optional notification that the system is running low on memory.
         * V8 uses these notifications to attempt to free memory.
         */
        void LowMemoryNotification();

        /**
         * Optional notification that a context has been disposed. V8 uses
         * these notifications to guide the GC heuristic. Returns the number
         * of context disposals - including this one - since the last time
         * V8 had a chance to clean up.
         *
         * The optional parameter |dependant_context| specifies whether the disposed
         * context was depending on state from other contexts or not.
         */
        int ContextDisposedNotification(bool dependant_context = true);

        /**
         * Optional notification that the isolate switched to the foreground.
         * V8 uses these notifications to guide heuristics.
         */
        void IsolateInForegroundNotification();

        /**
         * Optional notification that the isolate switched to the background.
         * V8 uses these notifications to guide heuristics.
         */
        void IsolateInBackgroundNotification();

        /**
         * Optional notification to tell V8 the current performance requirements
         * of the embedder based on RAIL.
         * V8 uses these notifications to guide heuristics.
         * This is an unfinished experimental feature. Semantics and implementation
         * may change frequently.
         */
        void SetRAILMode(RAILMode rail_mode);

        /**
         * Allows the host application to provide the address of a function that is
         * notified each time code is added, moved or removed.
         *
         * \param options options for the JIT code event handler.
         * \param event_handler the JIT code event handler, which will be invoked
         *     each time code is added, moved or removed.
         * \note \p event_handler won't get notified of existent code.
         * \note since code removal notifications are not currently issued, the
         *     \p event_handler may get notifications of code that overlaps earlier
         *     code notifications. This happens when code areas are reused, and the
         *     earlier overlapping code areas should therefore be discarded.
         * \note the events passed to \p event_handler and the strings they point to
         *     are not guaranteed to live past each call. The \p event_handler must
         *     copy strings and other parameters it needs to keep around.
         * \note the set of events declared in JitCodeEvent::EventType is expected to
         *     grow over time, and the JitCodeEvent structure is expected to accrue
         *     new members. The \p event_handler function must ignore event codes
         *     it does not recognize to maintain future compatibility.
         * \note Use Isolate::CreateParams to get events for code executed during
         *     Isolate setup.
         */
        void SetJitCodeEventHandler(JitCodeEventOptions options,
                                    JitCodeEventHandler event_handler);

        /**
         * Modifies the stack limit for this Isolate.
         *
         * \param stack_limit An address beyond which the Vm's stack may not grow.
         *
         * \note  If you are using threads then you should hold the V8::Locker lock
         *     while setting the stack limit and you must set a non-default stack
         *     limit separately for each thread.
         */
        void SetStackLimit(uintptr_t stack_limit);

        /**
         * Returns a memory range that can potentially contain jitted code.
         *
         * On Win64, embedders are advised to install function table callbacks for
         * these ranges, as default SEH won't be able to unwind through jitted code.
         *
         * The first page of the code range is reserved for the embedder and is
         * committed, writable, and executable.
         *
         * Might be empty on other platforms.
         *
         * https://code.google.com/p/v8/issues/detail?id=3598
         */
        void GetCodeRange(void** start, size_t* length_in_bytes);

        /** Set the callback to invoke in case of fatal errors. */
        void SetFatalErrorHandler(FatalErrorCallback that);

        /** Set the callback to invoke in case of OOM errors. */
        void SetOOMErrorHandler(OOMErrorCallback that);

        /**
         * Set the callback to invoke to check if code generation from
         * strings should be allowed.
         */
        void SetAllowCodeGenerationFromStringsCallback(
            AllowCodeGenerationFromStringsCallback callback);

        /**
        * Check if V8 is dead and therefore unusable.  This is the case after
        * fatal errors such as out-of-memory situations.
        */
        bool IsDead();

        /**
         * Adds a message listener.
         *
         * The same message listener can be added more than once and in that
         * case it will be called more than once for each message.
         *
         * If data is specified, it will be passed to the callback when it is called.
         * Otherwise, the exception object will be passed to the callback instead.
         */
        bool AddMessageListener(MessageCallback that,
                                Local<Value> data = Local<Value>());

        /**
         * Remove all message listeners from the specified callback function.
         */
        void RemoveMessageListeners(MessageCallback that);

        /** Callback function for reporting failed access checks.*/
        void SetFailedAccessCheckCallbackFunction(FailedAccessCheckCallback);

        /**
         * Tells V8 to capture current stack trace when uncaught exception occurs
         * and report it to the message listeners. The option is off by default.
         */
        void SetCaptureStackTraceForUncaughtExceptions(
            bool capture, int frame_limit = 10,
            StackTrace::StackTraceOptions options = StackTrace::kOverview);

        /**
         * Iterates through all external resources referenced from current isolate
         * heap.  GC is not invoked prior to iterating, therefore there is no
         * guarantee that visited objects are still alive.
         */
        void VisitExternalResources(ExternalResourceVisitor* visitor);

        /**
         * Iterates through all the persistent handles in the current isolate's heap
         * that have class_ids.
         */
        void VisitHandlesWithClassIds(PersistentHandleVisitor* visitor);

        /**
         * Iterates through all the persistent handles in the current isolate's heap
         * that have class_ids and are candidates to be marked as partially dependent
         * handles. This will visit handles to young objects created since the last
         * garbage collection but is free to visit an arbitrary superset of these
         * objects.
         */
        void VisitHandlesForPartialDependence(PersistentHandleVisitor* visitor);

        /**
         * Iterates through all the persistent handles in the current isolate's heap
         * that have class_ids and are weak to be marked as inactive if there is no
         * pending activity for the handle.
         */
        void VisitWeakHandles(PersistentHandleVisitor* visitor);

        /**
         * Check if this isolate is in use.
         * True if at least one thread Enter'ed this isolate.
         */
        bool IsInUse();

        Isolate() = delete;
        ~Isolate() = delete;
        Isolate(const Isolate&) = delete;
        Isolate& operator=(const Isolate&) = delete;
        void* operator new(size_t size) = delete;
        void operator delete(void*, size_t) = delete;

    private:
        template <class K, class V, class Traits>
        friend class PersistentValueMapBase;

        void SetObjectGroupId(internal::Object** object, UniqueId id);
        void SetReferenceFromGroup(UniqueId id, internal::Object** object);
        void SetReference(internal::Object** parent, internal::Object** child);
        void ReportExternalAllocationLimitReached();
};

class V8_EXPORT StartupData {
    public:
        const char* data;
        int raw_size;
};


/**
 * EntropySource is used as a callback function when v8 needs a source
 * of entropy.
 */
typedef bool (*EntropySource)(unsigned char* buffer, size_t length);

/**
 * ReturnAddressLocationResolver is used as a callback function when v8 is
 * resolving the location of a return address on the stack. Profilers that
 * change the return address on the stack can use this to resolve the stack
 * location to whereever the profiler stashed the original return address.
 *
 * \param return_addr_location A location on stack where a machine
 *    return address resides.
 * \returns Either return_addr_location, or else a pointer to the profiler's
 *    copy of the original return address.
 *
 * \note The resolver function must not cause garbage collection.
 */
typedef uintptr_t (*ReturnAddressLocationResolver)(
    uintptr_t return_addr_location);


/**
 * Container class for static utility functions.
 */
class V8_EXPORT V8 {
    public:
        /** Set the callback to invoke in case of fatal errors. */
        V8_INLINE static V8_DEPRECATED(
            "Use isolate version",
            void SetFatalErrorHandler(FatalErrorCallback that));

        /**
         * Set the callback to invoke to check if code generation from
         * strings should be allowed.
         */
        V8_INLINE static V8_DEPRECATED(
            "Use isolate version", void SetAllowCodeGenerationFromStringsCallback(
                AllowCodeGenerationFromStringsCallback that));

        /**
        * Check if V8 is dead and therefore unusable.  This is the case after
        * fatal errors such as out-of-memory situations.
        */
        V8_INLINE static V8_DEPRECATED("Use isolate version", bool IsDead());

        /**
         * Hand startup data to V8, in case the embedder has chosen to build
         * V8 with external startup data.
         *
         * Note:
         * - By default the startup data is linked into the V8 library, in which
         *   case this function is not meaningful.
         * - If this needs to be called, it needs to be called before V8
         *   tries to make use of its built-ins.
         * - To avoid unnecessary copies of data, V8 will point directly into the
         *   given data blob, so pretty please keep it around until V8 exit.
         * - Compression of the startup blob might be useful, but needs to
         *   handled entirely on the embedders' side.
         * - The call will abort if the data is invalid.
         */
        static void SetNativesDataBlob(StartupData* startup_blob);
        static void SetSnapshotDataBlob(StartupData* startup_blob);

        /**
         * Bootstrap an isolate and a context from scratch to create a startup
         * snapshot. Include the side-effects of running the optional script.
         * Returns { NULL, 0 } on failure.
         * The caller acquires ownership of the data array in the return value.
         */
        static StartupData CreateSnapshotDataBlob(const char* embedded_source = NULL);

        /**
         * Bootstrap an isolate and a context from the cold startup blob, run the
         * warm-up script to trigger code compilation. The side effects are then
         * discarded. The resulting startup snapshot will include compiled code.
         * Returns { NULL, 0 } on failure.
         * The caller acquires ownership of the data array in the return value.
         * The argument startup blob is untouched.
         */
        static StartupData WarmUpSnapshotDataBlob(StartupData cold_startup_blob,
                const char* warmup_source);

        /**
         * Adds a message listener.
         *
         * The same message listener can be added more than once and in that
         * case it will be called more than once for each message.
         *
         * If data is specified, it will be passed to the callback when it is called.
         * Otherwise, the exception object will be passed to the callback instead.
         */
        V8_INLINE static V8_DEPRECATED(
            "Use isolate version",
            bool AddMessageListener(MessageCallback that,
                                    Local<Value> data = Local<Value>()));

        /**
         * Remove all message listeners from the specified callback function.
         */
        V8_INLINE static V8_DEPRECATED(
            "Use isolate version", void RemoveMessageListeners(MessageCallback that));

        /**
         * Tells V8 to capture current stack trace when uncaught exception occurs
         * and report it to the message listeners. The option is off by default.
         */
        V8_INLINE static V8_DEPRECATED(
            "Use isolate version",
            void SetCaptureStackTraceForUncaughtExceptions(
                bool capture, int frame_limit = 10,
                StackTrace::StackTraceOptions options = StackTrace::kOverview));

        /**
         * Sets V8 flags from a string.
         */
        static void SetFlagsFromString(const char* str, int length);

        /**
         * Sets V8 flags from the command line.
         */
        static void SetFlagsFromCommandLine(int* argc,
                                            char** argv,
                                            bool remove_flags);

        /** Get the version string. */
        static const char* GetVersion();

        /** Callback function for reporting failed access checks.*/
        V8_INLINE static V8_DEPRECATED(
            "Use isolate version",
            void SetFailedAccessCheckCallbackFunction(FailedAccessCheckCallback));

        /**
         * Enables the host application to receive a notification before a
         * garbage collection.  Allocations are not allowed in the
         * callback function, you therefore cannot manipulate objects (set
         * or delete properties for example) since it is possible such
         * operations will result in the allocation of objects. It is possible
         * to specify the GCType filter for your callback. But it is not possible to
         * register the same callback function two times with different
         * GCType filters.
         */
        static V8_DEPRECATED(
            "Use isolate version",
            void AddGCPrologueCallback(GCCallback callback,
                                       GCType gc_type_filter = kGCTypeAll));

        /**
         * This function removes callback which was installed by
         * AddGCPrologueCallback function.
         */
        V8_INLINE static V8_DEPRECATED(
            "Use isolate version",
            void RemoveGCPrologueCallback(GCCallback callback));

        /**
         * Enables the host application to receive a notification after a
         * garbage collection.  Allocations are not allowed in the
         * callback function, you therefore cannot manipulate objects (set
         * or delete properties for example) since it is possible such
         * operations will result in the allocation of objects. It is possible
         * to specify the GCType filter for your callback. But it is not possible to
         * register the same callback function two times with different
         * GCType filters.
         */
        static V8_DEPRECATED(
            "Use isolate version",
            void AddGCEpilogueCallback(GCCallback callback,
                                       GCType gc_type_filter = kGCTypeAll));

        /**
         * This function removes callback which was installed by
         * AddGCEpilogueCallback function.
         */
        V8_INLINE static V8_DEPRECATED(
            "Use isolate version",
            void RemoveGCEpilogueCallback(GCCallback callback));

        /**
         * Initializes V8. This function needs to be called before the first Isolate
         * is created. It always returns true.
         */
        static bool Initialize();

        /**
         * Allows the host application to provide a callback which can be used
         * as a source of entropy for random number generators.
         */
        static void SetEntropySource(EntropySource source);

        /**
         * Allows the host application to provide a callback that allows v8 to
         * cooperate with a profiler that rewrites return addresses on stack.
         */
        static void SetReturnAddressLocationResolver(
            ReturnAddressLocationResolver return_address_resolver);

        /**
         * Forcefully terminate the current thread of JavaScript execution
         * in the given isolate.
         *
         * This method can be used by any thread even if that thread has not
         * acquired the V8 lock with a Locker object.
         *
         * \param isolate The isolate in which to terminate the current JS execution.
         */
        V8_INLINE static V8_DEPRECATED("Use isolate version",
                                       void TerminateExecution(Isolate* isolate));

        /**
         * Is V8 terminating JavaScript execution.
         *
         * Returns true if JavaScript execution is currently terminating
         * because of a call to TerminateExecution.  In that case there are
         * still JavaScript frames on the stack and the termination
         * exception is still active.
         *
         * \param isolate The isolate in which to check.
         */
        V8_INLINE static V8_DEPRECATED(
            "Use isolate version",
            bool IsExecutionTerminating(Isolate* isolate = NULL));

        /**
         * Resume execution capability in the given isolate, whose execution
         * was previously forcefully terminated using TerminateExecution().
         *
         * When execution is forcefully terminated using TerminateExecution(),
         * the isolate can not resume execution until all JavaScript frames
         * have propagated the uncatchable exception which is generated.  This
         * method allows the program embedding the engine to handle the
         * termination event and resume execution capability, even if
         * JavaScript frames remain on the stack.
         *
         * This method can be used by any thread even if that thread has not
         * acquired the V8 lock with a Locker object.
         *
         * \param isolate The isolate in which to resume execution capability.
         */
        V8_INLINE static V8_DEPRECATED(
            "Use isolate version", void CancelTerminateExecution(Isolate* isolate));

        /**
         * Releases any resources used by v8 and stops any utility threads
         * that may be running.  Note that disposing v8 is permanent, it
         * cannot be reinitialized.
         *
         * It should generally not be necessary to dispose v8 before exiting
         * a process, this should happen automatically.  It is only necessary
         * to use if the process needs the resources taken up by v8.
         */
        static bool Dispose();

        /**
         * Iterates through all external resources referenced from current isolate
         * heap.  GC is not invoked prior to iterating, therefore there is no
         * guarantee that visited objects are still alive.
         */
        V8_INLINE static V8_DEPRECATED(
            "Use isolate version",
            void VisitExternalResources(ExternalResourceVisitor* visitor));

        /**
         * Iterates through all the persistent handles in the current isolate's heap
         * that have class_ids.
         */
        V8_INLINE static V8_DEPRECATED(
            "Use isolate version",
            void VisitHandlesWithClassIds(PersistentHandleVisitor* visitor));

        /**
         * Iterates through all the persistent handles in isolate's heap that have
         * class_ids.
         */
        V8_INLINE static V8_DEPRECATED(
            "Use isolate version",
            void VisitHandlesWithClassIds(Isolate* isolate,
                                          PersistentHandleVisitor* visitor));

        /**
         * Iterates through all the persistent handles in the current isolate's heap
         * that have class_ids and are candidates to be marked as partially dependent
         * handles. This will visit handles to young objects created since the last
         * garbage collection but is free to visit an arbitrary superset of these
         * objects.
         */
        V8_INLINE static V8_DEPRECATED(
            "Use isolate version",
            void VisitHandlesForPartialDependence(Isolate* isolate,
                    PersistentHandleVisitor* visitor));

        /**
         * Initialize the ICU library bundled with V8. The embedder should only
         * invoke this method when using the bundled ICU. Returns true on success.
         *
         * If V8 was compiled with the ICU data in an external file, the location
         * of the data file has to be provided.
         */
        V8_DEPRECATE_SOON(
            "Use version with default location.",
            static bool InitializeICU(const char* icu_data_file = nullptr));

        /**
         * Initialize the ICU library bundled with V8. The embedder should only
         * invoke this method when using the bundled ICU. If V8 was compiled with
         * the ICU data in an external file and when the default location of that
         * file should be used, a path to the executable must be provided.
         * Returns true on success.
         *
         * The default is a file called icudtl.dat side-by-side with the executable.
         *
         * Optionally, the location of the data file can be provided to override the
         * default.
         */
        static bool InitializeICUDefaultLocation(const char* exec_path,
                const char* icu_data_file = nullptr);

        /**
         * Initialize the external startup data. The embedder only needs to
         * invoke this method when external startup data was enabled in a build.
         *
         * If V8 was compiled with the startup data in an external file, then
         * V8 needs to be given those external files during startup. There are
         * three ways to do this:
         * - InitializeExternalStartupData(const char*)
         *   This will look in the given directory for files "natives_blob.bin"
         *   and "snapshot_blob.bin" - which is what the default build calls them.
         * - InitializeExternalStartupData(const char*, const char*)
         *   As above, but will directly use the two given file names.
         * - Call SetNativesDataBlob, SetNativesDataBlob.
         *   This will read the blobs from the given data structures and will
         *   not perform any file IO.
         */
        static void InitializeExternalStartupData(const char* directory_path);
        static void InitializeExternalStartupData(const char* natives_blob,
                const char* snapshot_blob);
        /**
         * Sets the v8::Platform to use. This should be invoked before V8 is
         * initialized.
         */
        static void InitializePlatform(Platform* platform);

        /**
         * Clears all references to the v8::Platform. This should be invoked after
         * V8 was disposed.
         */
        static void ShutdownPlatform();

    private:
        V8();

        static internal::Object** GlobalizeReference(internal::Isolate* isolate,
                internal::Object** handle);
        static internal::Object** CopyPersistent(internal::Object** handle);
        static void DisposeGlobal(internal::Object** global_handle);
        static void MakeWeak(internal::Object** location, void* data,
                             WeakCallbackInfo<void>::Callback weak_callback,
                             WeakCallbackType type);
        static void MakeWeak(internal::Object** location, void* data,
                             // Must be 0 or -1.
                             int internal_field_index1,
                             // Must be 1 or -1.
                             int internal_field_index2,
                             WeakCallbackInfo<void>::Callback weak_callback);
        static void MakeWeak(internal::Object** * location_addr);
        static void* ClearWeak(internal::Object** location);
        static void Eternalize(Isolate* isolate,
                               Value* handle,
                               int* index);
        static Local<Value> GetEternal(Isolate* isolate, int index);

        template <class K, class V, class T>
        friend class PersistentValueMapBase;

        static void FromJustIsNothing();
        static void ToLocalEmpty();
        static void InternalFieldOutOfBounds(int index);
        template <class T> friend class Local;
        template <class T>
        friend class MaybeLocal;
        template <class T>
        friend class Maybe;
        template <class T>
        friend class WeakCallbackInfo;
        template <class T> friend class Eternal;
        template <class T> friend class PersistentBase;
        template <class T, class M> friend class Persistent;
        friend class Context;
};

/**
 * Helper class to create a snapshot data blob.
 */
class SnapshotCreator {
    public:
        enum class FunctionCodeHandling { kClear, kKeep };

        /**
         * Create and enter an isolate, and set it up for serialization.
         * The isolate is either created from scratch or from an existing snapshot.
         * The caller keeps ownership of the argument snapshot.
         * \param existing_blob existing snapshot from which to create this one.
         * \param external_references a null-terminated array of external references
         *        that must be equivalent to CreateParams::external_references.
         */
        SnapshotCreator(intptr_t* external_references = nullptr,
                        StartupData* existing_blob = nullptr);

        ~SnapshotCreator();

        /**
         * \returns the isolate prepared by the snapshot creator.
         */
        Isolate* GetIsolate();

        /**
         * Add a context to be included in the snapshot blob.
         * \returns the index of the context in the snapshot blob.
         */
        size_t AddContext(Local<Context> context);

        /**
         * Add a template to be included in the snapshot blob.
         * \returns the index of the template in the snapshot blob.
         */
        size_t AddTemplate(Local<Template> template_obj);

        /**
         * Created a snapshot data blob.
         * This must not be called from within a handle scope.
         * \param function_code_handling whether to include compiled function code
         *        in the snapshot.
         * \returns { nullptr, 0 } on failure, and a startup snapshot on success. The
         *        caller acquires ownership of the data array in the return value.
         */
        StartupData CreateBlob(FunctionCodeHandling function_code_handling);

        // Disallow copying and assigning.
        SnapshotCreator(const SnapshotCreator&) = delete;
        void operator=(const SnapshotCreator&) = delete;

    private:
        void* data_;
};

/**
 * A simple Maybe type, representing an object which may or may not have a
 * value, see https://hackage.haskell.org/package/base/docs/Data-Maybe.html.
 *
 * If an API method returns a Maybe<>, the API method can potentially fail
 * either because an exception is thrown, or because an exception is pending,
 * e.g. because a previous API call threw an exception that hasn't been caught
 * yet, or because a TerminateExecution exception was thrown. In that case, a
 * "Nothing" value is returned.
 */
template <class T>
class Maybe {
    public:
        V8_INLINE bool IsNothing() const {
            return !has_value_;
        }
        V8_INLINE bool IsJust() const {
            return has_value_;
        }

        // Will crash if the Maybe<> is nothing.
        V8_INLINE T ToChecked() const {
            return FromJust();
        }

        V8_WARN_UNUSED_RESULT V8_INLINE bool To(T* out) const {
            if (V8_LIKELY(IsJust())) {
                *out = value_;
            }
            return IsJust();
        }

        // Will crash if the Maybe<> is nothing.
        V8_INLINE T FromJust() const {
            if (V8_UNLIKELY(!IsJust())) {
                V8::FromJustIsNothing();
            }
            return value_;
        }

        V8_INLINE T FromMaybe(const T& default_value) const {
            return has_value_ ? value_ : default_value;
        }

        V8_INLINE bool operator==(const Maybe& other) const {
            return (IsJust() == other.IsJust()) &&
                   (!IsJust() || FromJust() == other.FromJust());
        }

        V8_INLINE bool operator!=(const Maybe& other) const {
            return !operator==(other);
        }

    private:
        Maybe() : has_value_(false) {}
        explicit Maybe(const T& t) : has_value_(true), value_(t) {}

        bool has_value_;
        T value_;

        template <class U>
        friend Maybe<U> Nothing();
        template <class U>
        friend Maybe<U> Just(const U& u);
};


template <class T>
inline Maybe<T> Nothing() {
    return Maybe<T>();
}


template <class T>
inline Maybe<T> Just(const T& t) {
    return Maybe<T>(t);
}


/**
 * An external exception handler.
 */
class V8_EXPORT TryCatch {
    public:
        /**
         * Creates a new try/catch block and registers it with v8.  Note that
         * all TryCatch blocks should be stack allocated because the memory
         * location itself is compared against JavaScript try/catch blocks.
         */
        V8_DEPRECATED("Use isolate version", TryCatch());

        /**
         * Creates a new try/catch block and registers it with v8.  Note that
         * all TryCatch blocks should be stack allocated because the memory
         * location itself is compared against JavaScript try/catch blocks.
         */
        TryCatch(Isolate* isolate);

        /**
         * Unregisters and deletes this try/catch block.
         */
        ~TryCatch();

        /**
         * Returns true if an exception has been caught by this try/catch block.
         */
        bool HasCaught() const;

        /**
         * For certain types of exceptions, it makes no sense to continue execution.
         *
         * If CanContinue returns false, the correct action is to perform any C++
         * cleanup needed and then return.  If CanContinue returns false and
         * HasTerminated returns true, it is possible to call
         * CancelTerminateExecution in order to continue calling into the engine.
         */
        bool CanContinue() const;

        /**
         * Returns true if an exception has been caught due to script execution
         * being terminated.
         *
         * There is no JavaScript representation of an execution termination
         * exception.  Such exceptions are thrown when the TerminateExecution
         * methods are called to terminate a long-running script.
         *
         * If such an exception has been thrown, HasTerminated will return true,
         * indicating that it is possible to call CancelTerminateExecution in order
         * to continue calling into the engine.
         */
        bool HasTerminated() const;

        /**
         * Throws the exception caught by this TryCatch in a way that avoids
         * it being caught again by this same TryCatch.  As with ThrowException
         * it is illegal to execute any JavaScript operations after calling
         * ReThrow; the caller must return immediately to where the exception
         * is caught.
         */
        Local<Value> ReThrow();

        /**
         * Returns the exception caught by this try/catch block.  If no exception has
         * been caught an empty handle is returned.
         *
         * The returned handle is valid until this TryCatch block has been destroyed.
         */
        Local<Value> Exception() const;

        /**
         * Returns the .stack property of the thrown object.  If no .stack
         * property is present an empty handle is returned.
         */
        V8_DEPRECATE_SOON("Use maybe version.", Local<Value> StackTrace() const);
        V8_WARN_UNUSED_RESULT MaybeLocal<Value> StackTrace(
            Local<Context> context) const;

        /**
         * Returns the message associated with this exception.  If there is
         * no message associated an empty handle is returned.
         *
         * The returned handle is valid until this TryCatch block has been
         * destroyed.
         */
        Local<v8::Message> Message() const;

        /**
         * Clears any exceptions that may have been caught by this try/catch block.
         * After this method has been called, HasCaught() will return false. Cancels
         * the scheduled exception if it is caught and ReThrow() is not called before.
         *
         * It is not necessary to clear a try/catch block before using it again; if
         * another exception is thrown the previously caught exception will just be
         * overwritten.  However, it is often a good idea since it makes it easier
         * to determine which operation threw a given exception.
         */
        void Reset();

        /**
         * Set verbosity of the external exception handler.
         *
         * By default, exceptions that are caught by an external exception
         * handler are not reported.  Call SetVerbose with true on an
         * external exception handler to have exceptions caught by the
         * handler reported as if they were not caught.
         */
        void SetVerbose(bool value);

        /**
         * Set whether or not this TryCatch should capture a Message object
         * which holds source information about where the exception
         * occurred.  True by default.
         */
        void SetCaptureMessage(bool value);

        /**
         * There are cases when the raw address of C++ TryCatch object cannot be
         * used for comparisons with addresses into the JS stack. The cases are:
         * 1) ARM, ARM64 and MIPS simulators which have separate JS stack.
         * 2) Address sanitizer allocates local C++ object in the heap when
         *    UseAfterReturn mode is enabled.
         * This method returns address that can be used for comparisons with
         * addresses into the JS stack. When neither simulator nor ASAN's
         * UseAfterReturn is enabled, then the address returned will be the address
         * of the C++ try catch handler itself.
         */
        static void* JSStackComparableAddress(v8::TryCatch* handler) {
            if (handler == NULL) {
                return NULL;
            }
            return handler->js_stack_comparable_address_;
        }

        TryCatch(const TryCatch&) = delete;
        void operator=(const TryCatch&) = delete;
        void* operator new(size_t size) = delete;
        void operator delete(void*, size_t) = delete;

    private:
        void ResetInternal();

        v8::internal::Isolate* isolate_;
        v8::TryCatch* next_;
        void* exception_;
        void* message_obj_;
        void* js_stack_comparable_address_;
        bool is_verbose_ : 1;
        bool can_continue_ : 1;
        bool capture_message_ : 1;
        bool rethrow_ : 1;
        bool has_terminated_ : 1;

        friend class v8::internal::Isolate;
};


// --- Context ---


/**
 * A container for extension names.
 */
class V8_EXPORT ExtensionConfiguration {
    public:
        ExtensionConfiguration() : name_count_(0), names_(NULL) { }
        ExtensionConfiguration(int name_count, const char* names[])
            : name_count_(name_count), names_(names) { }

        const char** begin() const {
            return &names_[0];
        }
        const char** end()  const {
            return &names_[name_count_];
        }

    private:
        const int name_count_;
        const char** names_;
};


/**
 * A sandboxed execution context with its own set of built-in objects
 * and functions.
 */
class V8_EXPORT Context {
    public:
        /**
         * Returns the global proxy object.
         *
         * Global proxy object is a thin wrapper whose prototype points to actual
         * context's global object with the properties like Object, etc. This is done
         * that way for security reasons (for more details see
         * https://wiki.mozilla.org/Gecko:SplitWindow).
         *
         * Please note that changes to global proxy object prototype most probably
         * would break VM---v8 expects only global object as a prototype of global
         * proxy object.
         */
        Local<Object> Global();

        /**
         * Detaches the global object from its context before
         * the global object can be reused to create a new context.
         */
        void DetachGlobal();

        /**
         * Creates a new context and returns a handle to the newly allocated
         * context.
         *
         * \param isolate The isolate in which to create the context.
         *
         * \param extensions An optional extension configuration containing
         * the extensions to be installed in the newly created context.
         *
         * \param global_template An optional object template from which the
         * global object for the newly created context will be created.
         *
         * \param global_object An optional global object to be reused for
         * the newly created context. This global object must have been
         * created by a previous call to Context::New with the same global
         * template. The state of the global object will be completely reset
         * and only object identify will remain.
         */
        static Local<Context> New(
            Isolate* isolate, ExtensionConfiguration* extensions = NULL,
            MaybeLocal<ObjectTemplate> global_template = MaybeLocal<ObjectTemplate>(),
            MaybeLocal<Value> global_object = MaybeLocal<Value>());

        static MaybeLocal<Context> FromSnapshot(
            Isolate* isolate, size_t context_snapshot_index,
            ExtensionConfiguration* extensions = nullptr,
            MaybeLocal<ObjectTemplate> global_template = MaybeLocal<ObjectTemplate>(),
            MaybeLocal<Value> global_object = MaybeLocal<Value>());

        /**
         * Returns an global object that isn't backed by an actual context.
         *
         * The global template needs to have access checks with handlers installed.
         * If an existing global object is passed in, the global object is detached
         * from its context.
         *
         * Note that this is different from a detached context where all accesses to
         * the global proxy will fail. Instead, the access check handlers are invoked.
         *
         * It is also not possible to detach an object returned by this method.
         * Instead, the access check handlers need to return nothing to achieve the
         * same effect.
         *
         * It is possible, however, to create a new context from the global object
         * returned by this method.
         */
        static MaybeLocal<Object> NewRemoteContext(
            Isolate* isolate, Local<ObjectTemplate> global_template,
            MaybeLocal<Value> global_object = MaybeLocal<Value>());

        /**
         * Sets the security token for the context.  To access an object in
         * another context, the security tokens must match.
         */
        void SetSecurityToken(Local<Value> token);

        /** Restores the security token to the default value. */
        void UseDefaultSecurityToken();

        /** Returns the security token of this context.*/
        Local<Value> GetSecurityToken();

        /**
         * Enter this context.  After entering a context, all code compiled
         * and run is compiled and run in this context.  If another context
         * is already entered, this old context is saved so it can be
         * restored when the new context is exited.
         */
        void Enter();

        /**
         * Exit this context.  Exiting the current context restores the
         * context that was in place when entering the current context.
         */
        void Exit();

        /** Returns an isolate associated with a current context. */
        v8::Isolate* GetIsolate();

        /**
         * The field at kDebugIdIndex is reserved for V8 debugger implementation.
         * The value is propagated to the scripts compiled in given Context and
         * can be used for filtering scripts.
         */
        enum EmbedderDataFields { kDebugIdIndex = 0 };

        /**
         * Gets the embedder data with the given index, which must have been set by a
         * previous call to SetEmbedderData with the same index. Note that index 0
         * currently has a special meaning for Chrome's debugger.
         */
        V8_INLINE Local<Value> GetEmbedderData(int index);

        /**
         * Gets the binding object used by V8 extras. Extra natives get a reference
         * to this object and can use it to "export" functionality by adding
         * properties. Extra natives can also "import" functionality by accessing
         * properties added by the embedder using the V8 API.
         */
        Local<Object> GetExtrasBindingObject();

        /**
         * Sets the embedder data with the given index, growing the data as
         * needed. Note that index 0 currently has a special meaning for Chrome's
         * debugger.
         */
        void SetEmbedderData(int index, Local<Value> value);

        /**
         * Gets a 2-byte-aligned native pointer from the embedder data with the given
         * index, which must have been set by a previous call to
         * SetAlignedPointerInEmbedderData with the same index. Note that index 0
         * currently has a special meaning for Chrome's debugger.
         */
        V8_INLINE void* GetAlignedPointerFromEmbedderData(int index);

        /**
         * Sets a 2-byte-aligned native pointer in the embedder data with the given
         * index, growing the data as needed. Note that index 0 currently has a
         * special meaning for Chrome's debugger.
         */
        void SetAlignedPointerInEmbedderData(int index, void* value);

        /**
         * Control whether code generation from strings is allowed. Calling
         * this method with false will disable 'eval' and the 'Function'
         * constructor for code running in this context. If 'eval' or the
         * 'Function' constructor are used an exception will be thrown.
         *
         * If code generation from strings is not allowed the
         * V8::AllowCodeGenerationFromStrings callback will be invoked if
         * set before blocking the call to 'eval' or the 'Function'
         * constructor. If that callback returns true, the call will be
         * allowed, otherwise an exception will be thrown. If no callback is
         * set an exception will be thrown.
         */
        void AllowCodeGenerationFromStrings(bool allow);

        /**
         * Returns true if code generation from strings is allowed for the context.
         * For more details see AllowCodeGenerationFromStrings(bool) documentation.
         */
        bool IsCodeGenerationFromStringsAllowed();

        /**
         * Sets the error description for the exception that is thrown when
         * code generation from strings is not allowed and 'eval' or the 'Function'
         * constructor are called.
         */
        void SetErrorMessageForCodeGenerationFromStrings(Local<String> message);

        /**
         * Estimate the memory in bytes retained by this context.
         */
        size_t EstimatedSize();

        /**
         * Stack-allocated class which sets the execution context for all
         * operations executed within a local scope.
         */
        class Scope {
            public:
                explicit V8_INLINE Scope(Local<Context> context) : context_(context) {
                    context_->Enter();
                }
                V8_INLINE ~Scope() {
                    context_->Exit();
                }

            private:
                Local<Context> context_;
        };

    private:
        friend class Value;
        friend class Script;
        friend class Object;
        friend class Function;

        Local<Value> SlowGetEmbedderData(int index);
        void* SlowGetAlignedPointerFromEmbedderData(int index);
};


/**
 * Multiple threads in V8 are allowed, but only one thread at a time is allowed
 * to use any given V8 isolate, see the comments in the Isolate class. The
 * definition of 'using a V8 isolate' includes accessing handles or holding onto
 * object pointers obtained from V8 handles while in the particular V8 isolate.
 * It is up to the user of V8 to ensure, perhaps with locking, that this
 * constraint is not violated. In addition to any other synchronization
 * mechanism that may be used, the v8::Locker and v8::Unlocker classes must be
 * used to signal thread switches to V8.
 *
 * v8::Locker is a scoped lock object. While it's active, i.e. between its
 * construction and destruction, the current thread is allowed to use the locked
 * isolate. V8 guarantees that an isolate can be locked by at most one thread at
 * any time. In other words, the scope of a v8::Locker is a critical section.
 *
 * Sample usage:
* \code
 * ...
 * {
 *   v8::Locker locker(isolate);
 *   v8::Isolate::Scope isolate_scope(isolate);
 *   ...
 *   // Code using V8 and isolate goes here.
 *   ...
 * } // Destructor called here
 * \endcode
 *
 * If you wish to stop using V8 in a thread A you can do this either by
 * destroying the v8::Locker object as above or by constructing a v8::Unlocker
 * object:
 *
 * \code
 * {
 *   isolate->Exit();
 *   v8::Unlocker unlocker(isolate);
 *   ...
 *   // Code not using V8 goes here while V8 can run in another thread.
 *   ...
 * } // Destructor called here.
 * isolate->Enter();
 * \endcode
 *
 * The Unlocker object is intended for use in a long-running callback from V8,
 * where you want to release the V8 lock for other threads to use.
 *
 * The v8::Locker is a recursive lock, i.e. you can lock more than once in a
 * given thread. This can be useful if you have code that can be called either
 * from code that holds the lock or from code that does not. The Unlocker is
 * not recursive so you can not have several Unlockers on the stack at once, and
 * you can not use an Unlocker in a thread that is not inside a Locker's scope.
 *
 * An unlocker will unlock several lockers if it has to and reinstate the
 * correct depth of locking on its destruction, e.g.:
 *
 * \code
 * // V8 not locked.
 * {
 *   v8::Locker locker(isolate);
 *   Isolate::Scope isolate_scope(isolate);
 *   // V8 locked.
 *   {
 *     v8::Locker another_locker(isolate);
 *     // V8 still locked (2 levels).
 *     {
 *       isolate->Exit();
 *       v8::Unlocker unlocker(isolate);
 *       // V8 not locked.
 *     }
 *     isolate->Enter();
 *     // V8 locked again (2 levels).
 *   }
 *   // V8 still locked (1 level).
 * }
 * // V8 Now no longer locked.
 * \endcode
 */
class V8_EXPORT Unlocker {
    public:
        /**
         * Initialize Unlocker for a given Isolate.
         */
        V8_INLINE explicit Unlocker(Isolate* isolate) {
            Initialize(isolate);
        }

        ~Unlocker();
    private:
        void Initialize(Isolate* isolate);

        internal::Isolate* isolate_;
};


class V8_EXPORT Locker {
    public:
        /**
         * Initialize Locker for a given Isolate.
         */
        V8_INLINE explicit Locker(Isolate* isolate) {
            Initialize(isolate);
        }

        ~Locker();

        /**
         * Returns whether or not the locker for a given isolate, is locked by the
         * current thread.
         */
        static bool IsLocked(Isolate* isolate);

        /**
         * Returns whether v8::Locker is being used by this V8 instance.
         */
        static bool IsActive();

        // Disallow copying and assigning.
        Locker(const Locker&) = delete;
        void operator=(const Locker&) = delete;

    private:
        void Initialize(Isolate* isolate);

        bool has_lock_;
        bool top_level_;
        internal::Isolate* isolate_;
};


// --- Implementation ---


namespace internal {

const int kApiPointerSize = sizeof(void*);  // NOLINT
const int kApiIntSize = sizeof(int);  // NOLINT
const int kApiInt64Size = sizeof(int64_t);  // NOLINT

// Tag information for HeapObject.
const int kHeapObjectTag = 1;
const int kHeapObjectTagSize = 2;
const intptr_t kHeapObjectTagMask = (1 << kHeapObjectTagSize) - 1;

// Tag information for Smi.
const int kSmiTag = 0;
const int kSmiTagSize = 1;
const intptr_t kSmiTagMask = (1 << kSmiTagSize) - 1;

template <size_t ptr_size> struct SmiTagging;

template<int kSmiShiftSize>
V8_INLINE internal::Object* IntToSmi(int value) {
    int smi_shift_bits = kSmiTagSize + kSmiShiftSize;
    uintptr_t tagged_value =
        (static_cast<uintptr_t>(value) << smi_shift_bits) | kSmiTag;
    return reinterpret_cast<internal::Object*>(tagged_value);
}

// Smi constants for 32-bit systems.
template <> struct SmiTagging<4> {
    enum { kSmiShiftSize = 0, kSmiValueSize = 31 };
    static int SmiShiftSize() {
        return kSmiShiftSize;
    }
    static int SmiValueSize() {
        return kSmiValueSize;
    }
    V8_INLINE static int SmiToInt(const internal::Object* value) {
        int shift_bits = kSmiTagSize + kSmiShiftSize;
        // Throw away top 32 bits and shift down (requires >> to be sign extending).
        return static_cast<int>(reinterpret_cast<intptr_t>(value)) >> shift_bits;
    }
    V8_INLINE static internal::Object* IntToSmi(int value) {
        return internal::IntToSmi<kSmiShiftSize>(value);
    }
    V8_INLINE static bool IsValidSmi(intptr_t value) {
        // To be representable as an tagged small integer, the two
        // most-significant bits of 'value' must be either 00 or 11 due to
        // sign-extension. To check this we add 01 to the two
        // most-significant bits, and check if the most-significant bit is 0
        //
        // CAUTION: The original code below:
        // bool result = ((value + 0x40000000) & 0x80000000) == 0;
        // may lead to incorrect results according to the C language spec, and
        // in fact doesn't work correctly with gcc4.1.1 in some cases: The
        // compiler may produce undefined results in case of signed integer
        // overflow. The computation must be done w/ unsigned ints.
        return static_cast<uintptr_t>(value + 0x40000000U) < 0x80000000U;
    }
};

// Smi constants for 64-bit systems.
template <> struct SmiTagging<8> {
    enum { kSmiShiftSize = 31, kSmiValueSize = 32 };
    static int SmiShiftSize() {
        return kSmiShiftSize;
    }
    static int SmiValueSize() {
        return kSmiValueSize;
    }
    V8_INLINE static int SmiToInt(const internal::Object* value) {
        int shift_bits = kSmiTagSize + kSmiShiftSize;
        // Shift down and throw away top 32 bits.
        return static_cast<int>(reinterpret_cast<intptr_t>(value) >> shift_bits);
    }
    V8_INLINE static internal::Object* IntToSmi(int value) {
        return internal::IntToSmi<kSmiShiftSize>(value);
    }
    V8_INLINE static bool IsValidSmi(intptr_t value) {
        // To be representable as a long smi, the value must be a 32-bit integer.
        return (value == static_cast<int32_t>(value));
    }
};

typedef SmiTagging<kApiPointerSize> PlatformSmiTagging;
const int kSmiShiftSize = PlatformSmiTagging::kSmiShiftSize;
const int kSmiValueSize = PlatformSmiTagging::kSmiValueSize;
V8_INLINE static bool SmiValuesAre31Bits() {
    return kSmiValueSize == 31;
}
V8_INLINE static bool SmiValuesAre32Bits() {
    return kSmiValueSize == 32;
}

/**
 * This class exports constants and functionality from within v8 that
 * is necessary to implement inline functions in the v8 api.  Don't
 * depend on functions and constants defined here.
 */
class Internals {
    public:
        // These values match non-compiler-dependent values defined within
        // the implementation of v8.
        static const int kHeapObjectMapOffset = 0;
        static const int kMapInstanceTypeAndBitFieldOffset =
            1 * kApiPointerSize + kApiIntSize;
        static const int kStringResourceOffset = 3 * kApiPointerSize;

        static const int kOddballKindOffset = 4 * kApiPointerSize + sizeof(double);
        static const int kForeignAddressOffset = kApiPointerSize;
        static const int kJSObjectHeaderSize = 3 * kApiPointerSize;
        static const int kFixedArrayHeaderSize = 2 * kApiPointerSize;
        static const int kContextHeaderSize = 2 * kApiPointerSize;
        static const int kContextEmbedderDataIndex = 5;
        static const int kFullStringRepresentationMask = 0x07;
        static const int kStringEncodingMask = 0x4;
        static const int kExternalTwoByteRepresentationTag = 0x02;
        static const int kExternalOneByteRepresentationTag = 0x06;

        static const int kIsolateEmbedderDataOffset = 0 * kApiPointerSize;
        static const int kExternalMemoryOffset = 4 * kApiPointerSize;
        static const int kExternalMemoryLimitOffset =
            kExternalMemoryOffset + kApiInt64Size;
        static const int kIsolateRootsOffset = kExternalMemoryLimitOffset +
                                               kApiInt64Size + kApiInt64Size +
                                               kApiPointerSize + kApiPointerSize;
        static const int kUndefinedValueRootIndex = 4;
        static const int kTheHoleValueRootIndex = 5;
        static const int kNullValueRootIndex = 6;
        static const int kTrueValueRootIndex = 7;
        static const int kFalseValueRootIndex = 8;
        static const int kEmptyStringRootIndex = 9;

        static const int kNodeClassIdOffset = 1 * kApiPointerSize;
        static const int kNodeFlagsOffset = 1 * kApiPointerSize + 3;
        static const int kNodeStateMask = 0x7;
        static const int kNodeStateIsWeakValue = 2;
        static const int kNodeStateIsPendingValue = 3;
        static const int kNodeStateIsNearDeathValue = 4;
        static const int kNodeIsIndependentShift = 3;
        static const int kNodeIsPartiallyDependentShift = 4;
        static const int kNodeIsActiveShift = 4;

        static const int kJSObjectType = 0xb9;
        static const int kJSApiObjectType = 0xb8;
        static const int kFirstNonstringType = 0x80;
        static const int kOddballType = 0x83;
        static const int kForeignType = 0x87;

        static const int kUndefinedOddballKind = 5;
        static const int kNullOddballKind = 3;

        static const uint32_t kNumIsolateDataSlots = 4;

        V8_EXPORT static void CheckInitializedImpl(v8::Isolate* isolate);
        V8_INLINE static void CheckInitialized(v8::Isolate* isolate) {
#ifdef V8_ENABLE_CHECKS
            CheckInitializedImpl(isolate);
#endif
        }

        V8_INLINE static bool HasHeapObjectTag(const internal::Object* value) {
            return ((reinterpret_cast<intptr_t>(value) & kHeapObjectTagMask) ==
                    kHeapObjectTag);
        }

        V8_INLINE static int SmiValue(const internal::Object* value) {
            return PlatformSmiTagging::SmiToInt(value);
        }

        V8_INLINE static internal::Object* IntToSmi(int value) {
            return PlatformSmiTagging::IntToSmi(value);
        }

        V8_INLINE static bool IsValidSmi(intptr_t value) {
            return PlatformSmiTagging::IsValidSmi(value);
        }

        V8_INLINE static int GetInstanceType(const internal::Object* obj) {
            typedef internal::Object O;
            O* map = ReadField<O*>(obj, kHeapObjectMapOffset);
            // Map::InstanceType is defined so that it will always be loaded into
            // the LS 8 bits of one 16-bit word, regardless of endianess.
            return ReadField<uint16_t>(map, kMapInstanceTypeAndBitFieldOffset) & 0xff;
        }

        V8_INLINE static int GetOddballKind(const internal::Object* obj) {
            typedef internal::Object O;
            return SmiValue(ReadField<O*>(obj, kOddballKindOffset));
        }

        V8_INLINE static bool IsExternalTwoByteString(int instance_type) {
            int representation = (instance_type & kFullStringRepresentationMask);
            return representation == kExternalTwoByteRepresentationTag;
        }

        V8_INLINE static uint8_t GetNodeFlag(internal::Object** obj, int shift) {
            uint8_t* addr = reinterpret_cast<uint8_t*>(obj) + kNodeFlagsOffset;
            return *addr & static_cast<uint8_t>(1U << shift);
        }

        V8_INLINE static void UpdateNodeFlag(internal::Object** obj,
                                             bool value, int shift) {
            uint8_t* addr = reinterpret_cast<uint8_t*>(obj) + kNodeFlagsOffset;
            uint8_t mask = static_cast<uint8_t>(1U << shift);
            *addr = static_cast<uint8_t>((*addr & ~mask) | (value << shift));
        }

        V8_INLINE static uint8_t GetNodeState(internal::Object** obj) {
            uint8_t* addr = reinterpret_cast<uint8_t*>(obj) + kNodeFlagsOffset;
            return *addr & kNodeStateMask;
        }

        V8_INLINE static void UpdateNodeState(internal::Object** obj,
                                              uint8_t value) {
            uint8_t* addr = reinterpret_cast<uint8_t*>(obj) + kNodeFlagsOffset;
            *addr = static_cast<uint8_t>((*addr & ~kNodeStateMask) | value);
        }

        V8_INLINE static void SetEmbedderData(v8::Isolate* isolate,
                                              uint32_t slot,
                                              void* data) {
            uint8_t* addr = reinterpret_cast<uint8_t*>(isolate) +
                            kIsolateEmbedderDataOffset + slot * kApiPointerSize;
            *reinterpret_cast<void**>(addr) = data;
        }

        V8_INLINE static void* GetEmbedderData(const v8::Isolate* isolate,
                                               uint32_t slot) {
            const uint8_t* addr = reinterpret_cast<const uint8_t*>(isolate) +
                                  kIsolateEmbedderDataOffset + slot * kApiPointerSize;
            return *reinterpret_cast<void* const*>(addr);
        }

        V8_INLINE static internal::Object** GetRoot(v8::Isolate* isolate,
                int index) {
            uint8_t* addr = reinterpret_cast<uint8_t*>(isolate) + kIsolateRootsOffset;
            return reinterpret_cast<internal::Object**>(addr + index * kApiPointerSize);
        }

        template <typename T>
        V8_INLINE static T ReadField(const internal::Object* ptr, int offset) {
            const uint8_t* addr =
                reinterpret_cast<const uint8_t*>(ptr) + offset - kHeapObjectTag;
            return *reinterpret_cast<const T*>(addr);
        }

        template <typename T>
        V8_INLINE static T ReadEmbedderData(const v8::Context* context, int index) {
            typedef internal::Object O;
            typedef internal::Internals I;
            O* ctx = *reinterpret_cast<O* const*>(context);
            int embedder_data_offset = I::kContextHeaderSize +
                                       (internal::kApiPointerSize * I::kContextEmbedderDataIndex);
            O* embedder_data = I::ReadField<O*>(ctx, embedder_data_offset);
            int value_offset =
                I::kFixedArrayHeaderSize + (internal::kApiPointerSize * index);
            return I::ReadField<T>(embedder_data, value_offset);
        }
};

}  // namespace internal


template <class T>
Local<T> Local<T>::New(Isolate* isolate, Local<T> that) {
    return New(isolate, that.val_);
}

template <class T>
Local<T> Local<T>::New(Isolate* isolate, const PersistentBase<T>& that) {
    return New(isolate, that.val_);
}


template <class T>
Local<T> Local<T>::New(Isolate* isolate, T* that) {
    if (that == NULL) {
        return Local<T>();
    }
    T* that_ptr = that;
    internal::Object** p = reinterpret_cast<internal::Object**>(that_ptr);
    return Local<T>(reinterpret_cast<T*>(HandleScope::CreateHandle(
            reinterpret_cast<internal::Isolate*>(isolate), *p)));
}


template<class T>
template<class S>
void Eternal<T>::Set(Isolate* isolate, Local<S> handle) {
    TYPE_CHECK(T, S);
    V8::Eternalize(isolate, reinterpret_cast<Value*>(*handle), &this->index_);
}


template<class T>
Local<T> Eternal<T>::Get(Isolate* isolate) {
    return Local<T>(reinterpret_cast<T*>(*V8::GetEternal(isolate, index_)));
}


template <class T>
Local<T> MaybeLocal<T>::ToLocalChecked() {
    if (V8_UNLIKELY(val_ == nullptr)) {
        V8::ToLocalEmpty();
    }
    return Local<T>(val_);
}


template <class T>
void* WeakCallbackInfo<T>::GetInternalField(int index) const {
#ifdef V8_ENABLE_CHECKS
    if (index < 0 || index >= kInternalFieldsInWeakCallback) {
        V8::InternalFieldOutOfBounds(index);
    }
#endif
    return internal_fields_[index];
}


template <class T>
T* PersistentBase<T>::New(Isolate* isolate, T* that) {
    if (that == NULL) {
        return NULL;
    }
    internal::Object** p = reinterpret_cast<internal::Object**>(that);
    return reinterpret_cast<T*>(
               V8::GlobalizeReference(reinterpret_cast<internal::Isolate*>(isolate),
                                      p));
}


template <class T, class M>
template <class S, class M2>
void Persistent<T, M>::Copy(const Persistent<S, M2>& that) {
    TYPE_CHECK(T, S);
    this->Reset();
    if (that.IsEmpty()) {
        return;
    }
    internal::Object** p = reinterpret_cast<internal::Object**>(that.val_);
    this->val_ = reinterpret_cast<T*>(V8::CopyPersistent(p));
    M::Copy(that, this);
}


template <class T>
bool PersistentBase<T>::IsIndependent() const {
    typedef internal::Internals I;
    if (this->IsEmpty()) {
        return false;
    }
    return I::GetNodeFlag(reinterpret_cast<internal::Object**>(this->val_),
                          I::kNodeIsIndependentShift);
}


template <class T>
bool PersistentBase<T>::IsNearDeath() const {
    typedef internal::Internals I;
    if (this->IsEmpty()) {
        return false;
    }
    uint8_t node_state =
        I::GetNodeState(reinterpret_cast<internal::Object**>(this->val_));
    return node_state == I::kNodeStateIsNearDeathValue ||
           node_state == I::kNodeStateIsPendingValue;
}


template <class T>
bool PersistentBase<T>::IsWeak() const {
    typedef internal::Internals I;
    if (this->IsEmpty()) {
        return false;
    }
    return I::GetNodeState(reinterpret_cast<internal::Object**>(this->val_)) ==
           I::kNodeStateIsWeakValue;
}


template <class T>
void PersistentBase<T>::Reset() {
    if (this->IsEmpty()) {
        return;
    }
    V8::DisposeGlobal(reinterpret_cast<internal::Object**>(this->val_));
    val_ = 0;
}


template <class T>
template <class S>
void PersistentBase<T>::Reset(Isolate* isolate, const Local<S>& other) {
    TYPE_CHECK(T, S);
    Reset();
    if (other.IsEmpty()) {
        return;
    }
    this->val_ = New(isolate, other.val_);
}


template <class T>
template <class S>
void PersistentBase<T>::Reset(Isolate* isolate,
                              const PersistentBase<S>& other) {
    TYPE_CHECK(T, S);
    Reset();
    if (other.IsEmpty()) {
        return;
    }
    this->val_ = New(isolate, other.val_);
}


template <class T>
template <typename P>
V8_INLINE void PersistentBase<T>::SetWeak(
    P* parameter, typename WeakCallbackInfo<P>::Callback callback,
    WeakCallbackType type) {
    typedef typename WeakCallbackInfo<void>::Callback Callback;
    V8::MakeWeak(reinterpret_cast<internal::Object**>(this->val_), parameter,
                 reinterpret_cast<Callback>(callback), type);
}

template <class T>
void PersistentBase<T>::SetWeak() {
    V8::MakeWeak(reinterpret_cast<internal::Object***>(&this->val_));
}

template <class T>
template <typename P>
P* PersistentBase<T>::ClearWeak() {
    return reinterpret_cast<P*>(
               V8::ClearWeak(reinterpret_cast<internal::Object**>(this->val_)));
}

template <class T>
void PersistentBase<T>::RegisterExternalReference(
    EmbedderReachableReferenceReporter* reporter) const {
    if (IsEmpty()) {
        return;
    }
    reporter->ReportExternalReference(this->val_);
}

template <class T>
void PersistentBase<T>::MarkIndependent() {
    typedef internal::Internals I;
    if (this->IsEmpty()) {
        return;
    }
    I::UpdateNodeFlag(reinterpret_cast<internal::Object**>(this->val_),
                      true,
                      I::kNodeIsIndependentShift);
}


template <class T>
void PersistentBase<T>::MarkPartiallyDependent() {
    typedef internal::Internals I;
    if (this->IsEmpty()) {
        return;
    }
    I::UpdateNodeFlag(reinterpret_cast<internal::Object**>(this->val_),
                      true,
                      I::kNodeIsPartiallyDependentShift);
}


template <class T>
void PersistentBase<T>::MarkActive() {
    typedef internal::Internals I;
    if (this->IsEmpty()) {
        return;
    }
    I::UpdateNodeFlag(reinterpret_cast<internal::Object**>(this->val_), true,
                      I::kNodeIsActiveShift);
}


template <class T>
void PersistentBase<T>::SetWrapperClassId(uint16_t class_id) {
    typedef internal::Internals I;
    if (this->IsEmpty()) {
        return;
    }
    internal::Object** obj = reinterpret_cast<internal::Object**>(this->val_);
    uint8_t* addr = reinterpret_cast<uint8_t*>(obj) + I::kNodeClassIdOffset;
    *reinterpret_cast<uint16_t*>(addr) = class_id;
}


template <class T>
uint16_t PersistentBase<T>::WrapperClassId() const {
    typedef internal::Internals I;
    if (this->IsEmpty()) {
        return 0;
    }
    internal::Object** obj = reinterpret_cast<internal::Object**>(this->val_);
    uint8_t* addr = reinterpret_cast<uint8_t*>(obj) + I::kNodeClassIdOffset;
    return *reinterpret_cast<uint16_t*>(addr);
}


template<typename T>
ReturnValue<T>::ReturnValue(internal::Object** slot) : value_(slot) {}

template<typename T>
template<typename S>
void ReturnValue<T>::Set(const Persistent<S>& handle) {
    TYPE_CHECK(T, S);
    if (V8_UNLIKELY(handle.IsEmpty())) {
        *value_ = GetDefaultValue();
    } else {
        *value_ = *reinterpret_cast<internal::Object**>(*handle);
    }
}

template <typename T>
template <typename S>
void ReturnValue<T>::Set(const Global<S>& handle) {
    TYPE_CHECK(T, S);
    if (V8_UNLIKELY(handle.IsEmpty())) {
        *value_ = GetDefaultValue();
    } else {
        *value_ = *reinterpret_cast<internal::Object**>(*handle);
    }
}

template <typename T>
template <typename S>
void ReturnValue<T>::Set(const Local<S> handle) {
    TYPE_CHECK(T, S);
    if (V8_UNLIKELY(handle.IsEmpty())) {
        *value_ = GetDefaultValue();
    } else {
        *value_ = *reinterpret_cast<internal::Object**>(*handle);
    }
}

template<typename T>
void ReturnValue<T>::Set(double i) {
    TYPE_CHECK(T, Number);
    Set(Number::New(GetIsolate(), i));
}

template<typename T>
void ReturnValue<T>::Set(int32_t i) {
    TYPE_CHECK(T, Integer);
    typedef internal::Internals I;
    if (V8_LIKELY(I::IsValidSmi(i))) {
        *value_ = I::IntToSmi(i);
        return;
    }
    Set(Integer::New(GetIsolate(), i));
}

template<typename T>
void ReturnValue<T>::Set(uint32_t i) {
    TYPE_CHECK(T, Integer);
    // Can't simply use INT32_MAX here for whatever reason.
    bool fits_into_int32_t = (i & (1U << 31)) == 0;
    if (V8_LIKELY(fits_into_int32_t)) {
        Set(static_cast<int32_t>(i));
        return;
    }
    Set(Integer::NewFromUnsigned(GetIsolate(), i));
}

template<typename T>
void ReturnValue<T>::Set(bool value) {
    TYPE_CHECK(T, Boolean);
    typedef internal::Internals I;
    int root_index;
    if (value) {
        root_index = I::kTrueValueRootIndex;
    } else {
        root_index = I::kFalseValueRootIndex;
    }
    *value_ = *I::GetRoot(GetIsolate(), root_index);
}

template<typename T>
void ReturnValue<T>::SetNull() {
    TYPE_CHECK(T, Primitive);
    typedef internal::Internals I;
    *value_ = *I::GetRoot(GetIsolate(), I::kNullValueRootIndex);
}

template<typename T>
void ReturnValue<T>::SetUndefined() {
    TYPE_CHECK(T, Primitive);
    typedef internal::Internals I;
    *value_ = *I::GetRoot(GetIsolate(), I::kUndefinedValueRootIndex);
}

template<typename T>
void ReturnValue<T>::SetEmptyString() {
    TYPE_CHECK(T, String);
    typedef internal::Internals I;
    *value_ = *I::GetRoot(GetIsolate(), I::kEmptyStringRootIndex);
}

template <typename T>
Isolate* ReturnValue<T>::GetIsolate() const {
    // Isolate is always the pointer below the default value on the stack.
    return *reinterpret_cast<Isolate**>(&value_[-2]);
}

template <typename T>
Local<Value> ReturnValue<T>::Get() const {
    typedef internal::Internals I;
    if (*value_ == *I::GetRoot(GetIsolate(), I::kTheHoleValueRootIndex)) {
        return Local<Value>(*Undefined(GetIsolate()));
    }
    return Local<Value>::New(GetIsolate(), reinterpret_cast<Value*>(value_));
}

template <typename T>
template <typename S>
void ReturnValue<T>::Set(S* whatever) {
    // Uncompilable to prevent inadvertent misuse.
    TYPE_CHECK(S*, Primitive);
}

template<typename T>
internal::Object* ReturnValue<T>::GetDefaultValue() {
    // Default value is always the pointer below value_ on the stack.
    return value_[-1];
}

template <typename T>
FunctionCallbackInfo<T>::FunctionCallbackInfo(internal::Object** implicit_args,
        internal::Object** values,
        int length)
    : implicit_args_(implicit_args), values_(values), length_(length) {}

template<typename T>
Local<Value> FunctionCallbackInfo<T>::operator[](int i) const {
    if (i < 0 || length_ <= i) {
        return Local<Value>(*Undefined(GetIsolate()));
    }
    return Local<Value>(reinterpret_cast<Value*>(values_ - i));
}


template<typename T>
Local<Function> FunctionCallbackInfo<T>::Callee() const {
    return Local<Function>(reinterpret_cast<Function*>(
                               &implicit_args_[kCalleeIndex]));
}


template<typename T>
Local<Object> FunctionCallbackInfo<T>::This() const {
    return Local<Object>(reinterpret_cast<Object*>(values_ + 1));
}


template<typename T>
Local<Object> FunctionCallbackInfo<T>::Holder() const {
    return Local<Object>(reinterpret_cast<Object*>(
                             &implicit_args_[kHolderIndex]));
}

template <typename T>
Local<Value> FunctionCallbackInfo<T>::NewTarget() const {
    return Local<Value>(
               reinterpret_cast<Value*>(&implicit_args_[kNewTargetIndex]));
}

template <typename T>
Local<Value> FunctionCallbackInfo<T>::Data() const {
    return Local<Value>(reinterpret_cast<Value*>(&implicit_args_[kDataIndex]));
}


template<typename T>
Isolate* FunctionCallbackInfo<T>::GetIsolate() const {
    return *reinterpret_cast<Isolate**>(&implicit_args_[kIsolateIndex]);
}


template<typename T>
ReturnValue<T> FunctionCallbackInfo<T>::GetReturnValue() const {
    return ReturnValue<T>(&implicit_args_[kReturnValueIndex]);
}


template<typename T>
bool FunctionCallbackInfo<T>::IsConstructCall() const {
    return !NewTarget()->IsUndefined();
}


template<typename T>
int FunctionCallbackInfo<T>::Length() const {
    return length_;
}

ScriptOrigin::ScriptOrigin(Local<Value> resource_name,
                           Local<Integer> resource_line_offset,
                           Local<Integer> resource_column_offset,
                           Local<Boolean> resource_is_shared_cross_origin,
                           Local<Integer> script_id,
                           Local<Boolean> resource_is_embedder_debug_script,
                           Local<Value> source_map_url,
                           Local<Boolean> resource_is_opaque)
    : resource_name_(resource_name),
      resource_line_offset_(resource_line_offset),
      resource_column_offset_(resource_column_offset),
      options_(!resource_is_embedder_debug_script.IsEmpty() &&
               resource_is_embedder_debug_script->IsTrue(),
               !resource_is_shared_cross_origin.IsEmpty() &&
               resource_is_shared_cross_origin->IsTrue(),
               !resource_is_opaque.IsEmpty() && resource_is_opaque->IsTrue()),
      script_id_(script_id),
      source_map_url_(source_map_url) {}

Local<Value> ScriptOrigin::ResourceName() const {
    return resource_name_;
}


Local<Integer> ScriptOrigin::ResourceLineOffset() const {
    return resource_line_offset_;
}


Local<Integer> ScriptOrigin::ResourceColumnOffset() const {
    return resource_column_offset_;
}


Local<Integer> ScriptOrigin::ScriptID() const {
    return script_id_;
}


Local<Value> ScriptOrigin::SourceMapUrl() const {
    return source_map_url_;
}


ScriptCompiler::Source::Source(Local<String> string, const ScriptOrigin& origin,
                               CachedData* data)
    : source_string(string),
      resource_name(origin.ResourceName()),
      resource_line_offset(origin.ResourceLineOffset()),
      resource_column_offset(origin.ResourceColumnOffset()),
      resource_options(origin.Options()),
      source_map_url(origin.SourceMapUrl()),
      cached_data(data) {}


ScriptCompiler::Source::Source(Local<String> string,
                               CachedData* data)
    : source_string(string), cached_data(data) {}


ScriptCompiler::Source::~Source() {
    delete cached_data;
}


const ScriptCompiler::CachedData* ScriptCompiler::Source::GetCachedData()
const {
    return cached_data;
}


Local<Boolean> Boolean::New(Isolate* isolate, bool value) {
    return value ? True(isolate) : False(isolate);
}


void Template::Set(Isolate* isolate, const char* name, v8::Local<Data> value) {
    Set(v8::String::NewFromUtf8(isolate, name, NewStringType::kNormal)
        .ToLocalChecked(),
        value);
}


Local<Value> Object::GetInternalField(int index) {
#ifndef V8_ENABLE_CHECKS
    typedef internal::Object O;
    typedef internal::HeapObject HO;
    typedef internal::Internals I;
    O* obj = *reinterpret_cast<O**>(this);
    // Fast path: If the object is a plain JSObject, which is the common case, we
    // know where to find the internal fields and can return the value directly.
    auto instance_type = I::GetInstanceType(obj);
    if (instance_type == I::kJSObjectType ||
            instance_type == I::kJSApiObjectType) {
        int offset = I::kJSObjectHeaderSize + (internal::kApiPointerSize * index);
        O* value = I::ReadField<O*>(obj, offset);
        O** result = HandleScope::CreateHandle(reinterpret_cast<HO*>(obj), value);
        return Local<Value>(reinterpret_cast<Value*>(result));
    }
#endif
    return SlowGetInternalField(index);
}


void* Object::GetAlignedPointerFromInternalField(int index) {
#ifndef V8_ENABLE_CHECKS
    typedef internal::Object O;
    typedef internal::Internals I;
    O* obj = *reinterpret_cast<O**>(this);
    // Fast path: If the object is a plain JSObject, which is the common case, we
    // know where to find the internal fields and can return the value directly.
    auto instance_type = I::GetInstanceType(obj);
    if (V8_LIKELY(instance_type == I::kJSObjectType ||
                  instance_type == I::kJSApiObjectType)) {
        int offset = I::kJSObjectHeaderSize + (internal::kApiPointerSize * index);
        return I::ReadField<void*>(obj, offset);
    }
#endif
    return SlowGetAlignedPointerFromInternalField(index);
}

String* String::Cast(v8::Value* value) {
#ifdef V8_ENABLE_CHECKS
    CheckCast(value);
#endif
    return static_cast<String*>(value);
}


Local<String> String::Empty(Isolate* isolate) {
    typedef internal::Object* S;
    typedef internal::Internals I;
    I::CheckInitialized(isolate);
    S* slot = I::GetRoot(isolate, I::kEmptyStringRootIndex);
    return Local<String>(reinterpret_cast<String*>(slot));
}


String::ExternalStringResource* String::GetExternalStringResource() const {
    typedef internal::Object O;
    typedef internal::Internals I;
    O* obj = *reinterpret_cast<O* const*>(this);
    String::ExternalStringResource* result;
    if (I::IsExternalTwoByteString(I::GetInstanceType(obj))) {
        void* value = I::ReadField<void*>(obj, I::kStringResourceOffset);
        result = reinterpret_cast<String::ExternalStringResource*>(value);
    } else {
        result = NULL;
    }
#ifdef V8_ENABLE_CHECKS
    VerifyExternalStringResource(result);
#endif
    return result;
}


String::ExternalStringResourceBase* String::GetExternalStringResourceBase(
    String::Encoding* encoding_out) const {
    typedef internal::Object O;
    typedef internal::Internals I;
    O* obj = *reinterpret_cast<O* const*>(this);
    int type = I::GetInstanceType(obj) & I::kFullStringRepresentationMask;
    *encoding_out = static_cast<Encoding>(type & I::kStringEncodingMask);
    ExternalStringResourceBase* resource = NULL;
    if (type == I::kExternalOneByteRepresentationTag ||
            type == I::kExternalTwoByteRepresentationTag) {
        void* value = I::ReadField<void*>(obj, I::kStringResourceOffset);
        resource = static_cast<ExternalStringResourceBase*>(value);
    }
#ifdef V8_ENABLE_CHECKS
    VerifyExternalStringResourceBase(resource, *encoding_out);
#endif
    return resource;
}


bool Value::IsUndefined() const {
#ifdef V8_ENABLE_CHECKS
    return FullIsUndefined();
#else
    return QuickIsUndefined();
#endif
}

bool Value::QuickIsUndefined() const {
    typedef internal::Object O;
    typedef internal::Internals I;
    O* obj = *reinterpret_cast<O* const*>(this);
    if (!I::HasHeapObjectTag(obj)) {
        return false;
    }
    if (I::GetInstanceType(obj) != I::kOddballType) {
        return false;
    }
    return (I::GetOddballKind(obj) == I::kUndefinedOddballKind);
}


bool Value::IsNull() const {
#ifdef V8_ENABLE_CHECKS
    return FullIsNull();
#else
    return QuickIsNull();
#endif
}

bool Value::QuickIsNull() const {
    typedef internal::Object O;
    typedef internal::Internals I;
    O* obj = *reinterpret_cast<O* const*>(this);
    if (!I::HasHeapObjectTag(obj)) {
        return false;
    }
    if (I::GetInstanceType(obj) != I::kOddballType) {
        return false;
    }
    return (I::GetOddballKind(obj) == I::kNullOddballKind);
}


bool Value::IsString() const {
#ifdef V8_ENABLE_CHECKS
    return FullIsString();
#else
    return QuickIsString();
#endif
}

bool Value::QuickIsString() const {
    typedef internal::Object O;
    typedef internal::Internals I;
    O* obj = *reinterpret_cast<O* const*>(this);
    if (!I::HasHeapObjectTag(obj)) {
        return false;
    }
    return (I::GetInstanceType(obj) < I::kFirstNonstringType);
}


template <class T> Value* Value::Cast(T* value) {
    return static_cast<Value*>(value);
}


Local<Boolean> Value::ToBoolean() const {
    return ToBoolean(Isolate::GetCurrent()->GetCurrentContext())
           .FromMaybe(Local<Boolean>());
}


Local<Number> Value::ToNumber() const {
    return ToNumber(Isolate::GetCurrent()->GetCurrentContext())
           .FromMaybe(Local<Number>());
}


Local<String> Value::ToString() const {
    return ToString(Isolate::GetCurrent()->GetCurrentContext())
           .FromMaybe(Local<String>());
}


Local<String> Value::ToDetailString() const {
    return ToDetailString(Isolate::GetCurrent()->GetCurrentContext())
           .FromMaybe(Local<String>());
}


Local<Object> Value::ToObject() const {
    return ToObject(Isolate::GetCurrent()->GetCurrentContext())
           .FromMaybe(Local<Object>());
}


Local<Integer> Value::ToInteger() const {
    return ToInteger(Isolate::GetCurrent()->GetCurrentContext())
           .FromMaybe(Local<Integer>());
}


Local<Uint32> Value::ToUint32() const {
    return ToUint32(Isolate::GetCurrent()->GetCurrentContext())
           .FromMaybe(Local<Uint32>());
}


Local<Int32> Value::ToInt32() const {
    return ToInt32(Isolate::GetCurrent()->GetCurrentContext())
           .FromMaybe(Local<Int32>());
}


Boolean* Boolean::Cast(v8::Value* value) {
#ifdef V8_ENABLE_CHECKS
    CheckCast(value);
#endif
    return static_cast<Boolean*>(value);
}


Name* Name::Cast(v8::Value* value) {
#ifdef V8_ENABLE_CHECKS
    CheckCast(value);
#endif
    return static_cast<Name*>(value);
}


Symbol* Symbol::Cast(v8::Value* value) {
#ifdef V8_ENABLE_CHECKS
    CheckCast(value);
#endif
    return static_cast<Symbol*>(value);
}


Number* Number::Cast(v8::Value* value) {
#ifdef V8_ENABLE_CHECKS
    CheckCast(value);
#endif
    return static_cast<Number*>(value);
}


Integer* Integer::Cast(v8::Value* value) {
#ifdef V8_ENABLE_CHECKS
    CheckCast(value);
#endif
    return static_cast<Integer*>(value);
}


Int32* Int32::Cast(v8::Value* value) {
#ifdef V8_ENABLE_CHECKS
    CheckCast(value);
#endif
    return static_cast<Int32*>(value);
}


Uint32* Uint32::Cast(v8::Value* value) {
#ifdef V8_ENABLE_CHECKS
    CheckCast(value);
#endif
    return static_cast<Uint32*>(value);
}


Date* Date::Cast(v8::Value* value) {
#ifdef V8_ENABLE_CHECKS
    CheckCast(value);
#endif
    return static_cast<Date*>(value);
}


StringObject* StringObject::Cast(v8::Value* value) {
#ifdef V8_ENABLE_CHECKS
    CheckCast(value);
#endif
    return static_cast<StringObject*>(value);
}


SymbolObject* SymbolObject::Cast(v8::Value* value) {
#ifdef V8_ENABLE_CHECKS
    CheckCast(value);
#endif
    return static_cast<SymbolObject*>(value);
}


NumberObject* NumberObject::Cast(v8::Value* value) {
#ifdef V8_ENABLE_CHECKS
    CheckCast(value);
#endif
    return static_cast<NumberObject*>(value);
}


BooleanObject* BooleanObject::Cast(v8::Value* value) {
#ifdef V8_ENABLE_CHECKS
    CheckCast(value);
#endif
    return static_cast<BooleanObject*>(value);
}


RegExp* RegExp::Cast(v8::Value* value) {
#ifdef V8_ENABLE_CHECKS
    CheckCast(value);
#endif
    return static_cast<RegExp*>(value);
}


Object* Object::Cast(v8::Value* value) {
#ifdef V8_ENABLE_CHECKS
    CheckCast(value);
#endif
    return static_cast<Object*>(value);
}


Array* Array::Cast(v8::Value* value) {
#ifdef V8_ENABLE_CHECKS
    CheckCast(value);
#endif
    return static_cast<Array*>(value);
}


Map* Map::Cast(v8::Value* value) {
#ifdef V8_ENABLE_CHECKS
    CheckCast(value);
#endif
    return static_cast<Map*>(value);
}


Set* Set::Cast(v8::Value* value) {
#ifdef V8_ENABLE_CHECKS
    CheckCast(value);
#endif
    return static_cast<Set*>(value);
}


Promise* Promise::Cast(v8::Value* value) {
#ifdef V8_ENABLE_CHECKS
    CheckCast(value);
#endif
    return static_cast<Promise*>(value);
}


Proxy* Proxy::Cast(v8::Value* value) {
#ifdef V8_ENABLE_CHECKS
    CheckCast(value);
#endif
    return static_cast<Proxy*>(value);
}

WasmCompiledModule* WasmCompiledModule::Cast(v8::Value* value) {
#ifdef V8_ENABLE_CHECKS
    CheckCast(value);
#endif
    return static_cast<WasmCompiledModule*>(value);
}

Promise::Resolver* Promise::Resolver::Cast(v8::Value* value) {
#ifdef V8_ENABLE_CHECKS
    CheckCast(value);
#endif
    return static_cast<Promise::Resolver*>(value);
}


ArrayBuffer* ArrayBuffer::Cast(v8::Value* value) {
#ifdef V8_ENABLE_CHECKS
    CheckCast(value);
#endif
    return static_cast<ArrayBuffer*>(value);
}


ArrayBufferView* ArrayBufferView::Cast(v8::Value* value) {
#ifdef V8_ENABLE_CHECKS
    CheckCast(value);
#endif
    return static_cast<ArrayBufferView*>(value);
}


TypedArray* TypedArray::Cast(v8::Value* value) {
#ifdef V8_ENABLE_CHECKS
    CheckCast(value);
#endif
    return static_cast<TypedArray*>(value);
}


Uint8Array* Uint8Array::Cast(v8::Value* value) {
#ifdef V8_ENABLE_CHECKS
    CheckCast(value);
#endif
    return static_cast<Uint8Array*>(value);
}


Int8Array* Int8Array::Cast(v8::Value* value) {
#ifdef V8_ENABLE_CHECKS
    CheckCast(value);
#endif
    return static_cast<Int8Array*>(value);
}


Uint16Array* Uint16Array::Cast(v8::Value* value) {
#ifdef V8_ENABLE_CHECKS
    CheckCast(value);
#endif
    return static_cast<Uint16Array*>(value);
}


Int16Array* Int16Array::Cast(v8::Value* value) {
#ifdef V8_ENABLE_CHECKS
    CheckCast(value);
#endif
    return static_cast<Int16Array*>(value);
}


Uint32Array* Uint32Array::Cast(v8::Value* value) {
#ifdef V8_ENABLE_CHECKS
    CheckCast(value);
#endif
    return static_cast<Uint32Array*>(value);
}


Int32Array* Int32Array::Cast(v8::Value* value) {
#ifdef V8_ENABLE_CHECKS
    CheckCast(value);
#endif
    return static_cast<Int32Array*>(value);
}


Float32Array* Float32Array::Cast(v8::Value* value) {
#ifdef V8_ENABLE_CHECKS
    CheckCast(value);
#endif
    return static_cast<Float32Array*>(value);
}


Float64Array* Float64Array::Cast(v8::Value* value) {
#ifdef V8_ENABLE_CHECKS
    CheckCast(value);
#endif
    return static_cast<Float64Array*>(value);
}


Uint8ClampedArray* Uint8ClampedArray::Cast(v8::Value* value) {
#ifdef V8_ENABLE_CHECKS
    CheckCast(value);
#endif
    return static_cast<Uint8ClampedArray*>(value);
}


DataView* DataView::Cast(v8::Value* value) {
#ifdef V8_ENABLE_CHECKS
    CheckCast(value);
#endif
    return static_cast<DataView*>(value);
}


SharedArrayBuffer* SharedArrayBuffer::Cast(v8::Value* value) {
#ifdef V8_ENABLE_CHECKS
    CheckCast(value);
#endif
    return static_cast<SharedArrayBuffer*>(value);
}


Function* Function::Cast(v8::Value* value) {
#ifdef V8_ENABLE_CHECKS
    CheckCast(value);
#endif
    return static_cast<Function*>(value);
}


External* External::Cast(v8::Value* value) {
#ifdef V8_ENABLE_CHECKS
    CheckCast(value);
#endif
    return static_cast<External*>(value);
}


template<typename T>
Isolate* PropertyCallbackInfo<T>::GetIsolate() const {
    return *reinterpret_cast<Isolate**>(&args_[kIsolateIndex]);
}


template<typename T>
Local<Value> PropertyCallbackInfo<T>::Data() const {
    return Local<Value>(reinterpret_cast<Value*>(&args_[kDataIndex]));
}


template<typename T>
Local<Object> PropertyCallbackInfo<T>::This() const {
    return Local<Object>(reinterpret_cast<Object*>(&args_[kThisIndex]));
}


template<typename T>
Local<Object> PropertyCallbackInfo<T>::Holder() const {
    return Local<Object>(reinterpret_cast<Object*>(&args_[kHolderIndex]));
}


template<typename T>
ReturnValue<T> PropertyCallbackInfo<T>::GetReturnValue() const {
    return ReturnValue<T>(&args_[kReturnValueIndex]);
}

template <typename T>
bool PropertyCallbackInfo<T>::ShouldThrowOnError() const {
    typedef internal::Internals I;
    return args_[kShouldThrowOnErrorIndex] != I::IntToSmi(0);
}


Local<Primitive> Undefined(Isolate* isolate) {
    typedef internal::Object* S;
    typedef internal::Internals I;
    I::CheckInitialized(isolate);
    S* slot = I::GetRoot(isolate, I::kUndefinedValueRootIndex);
    return Local<Primitive>(reinterpret_cast<Primitive*>(slot));
}


Local<Primitive> Null(Isolate* isolate) {
    typedef internal::Object* S;
    typedef internal::Internals I;
    I::CheckInitialized(isolate);
    S* slot = I::GetRoot(isolate, I::kNullValueRootIndex);
    return Local<Primitive>(reinterpret_cast<Primitive*>(slot));
}


Local<Boolean> True(Isolate* isolate) {
    typedef internal::Object* S;
    typedef internal::Internals I;
    I::CheckInitialized(isolate);
    S* slot = I::GetRoot(isolate, I::kTrueValueRootIndex);
    return Local<Boolean>(reinterpret_cast<Boolean*>(slot));
}


Local<Boolean> False(Isolate* isolate) {
    typedef internal::Object* S;
    typedef internal::Internals I;
    I::CheckInitialized(isolate);
    S* slot = I::GetRoot(isolate, I::kFalseValueRootIndex);
    return Local<Boolean>(reinterpret_cast<Boolean*>(slot));
}


void Isolate::SetData(uint32_t slot, void* data) {
    typedef internal::Internals I;
    I::SetEmbedderData(this, slot, data);
}


void* Isolate::GetData(uint32_t slot) {
    typedef internal::Internals I;
    return I::GetEmbedderData(this, slot);
}


uint32_t Isolate::GetNumberOfDataSlots() {
    typedef internal::Internals I;
    return I::kNumIsolateDataSlots;
}


int64_t Isolate::AdjustAmountOfExternalAllocatedMemory(
    int64_t change_in_bytes) {
    typedef internal::Internals I;
    int64_t* external_memory = reinterpret_cast<int64_t*>(
                                   reinterpret_cast<uint8_t*>(this) + I::kExternalMemoryOffset);
    const int64_t external_memory_limit = *reinterpret_cast<int64_t*>(
            reinterpret_cast<uint8_t*>(this) + I::kExternalMemoryLimitOffset);
    const int64_t amount = *external_memory + change_in_bytes;
    *external_memory = amount;
    if (change_in_bytes > 0 && amount > external_memory_limit) {
        ReportExternalAllocationLimitReached();
    }
    return *external_memory;
}


template<typename T>
void Isolate::SetObjectGroupId(const Persistent<T>& object,
                               UniqueId id) {
    TYPE_CHECK(Value, T);
    SetObjectGroupId(reinterpret_cast<v8::internal::Object**>(object.val_), id);
}


template<typename T>
void Isolate::SetReferenceFromGroup(UniqueId id,
                                    const Persistent<T>& object) {
    TYPE_CHECK(Value, T);
    SetReferenceFromGroup(id,
                          reinterpret_cast<v8::internal::Object**>(object.val_));
}


template<typename T, typename S>
void Isolate::SetReference(const Persistent<T>& parent,
                           const Persistent<S>& child) {
    TYPE_CHECK(Object, T);
    TYPE_CHECK(Value, S);
    SetReference(reinterpret_cast<v8::internal::Object**>(parent.val_),
                 reinterpret_cast<v8::internal::Object**>(child.val_));
}


Local<Value> Context::GetEmbedderData(int index) {
#ifndef V8_ENABLE_CHECKS
    typedef internal::Object O;
    typedef internal::HeapObject HO;
    typedef internal::Internals I;
    HO* context = *reinterpret_cast<HO**>(this);
    O** result =
        HandleScope::CreateHandle(context, I::ReadEmbedderData<O*>(this, index));
    return Local<Value>(reinterpret_cast<Value*>(result));
#else
    return SlowGetEmbedderData(index);
#endif
}


void* Context::GetAlignedPointerFromEmbedderData(int index) {
#ifndef V8_ENABLE_CHECKS
    typedef internal::Internals I;
    return I::ReadEmbedderData<void*>(this, index);
#else
    return SlowGetAlignedPointerFromEmbedderData(index);
#endif
}


void V8::SetAllowCodeGenerationFromStringsCallback(
    AllowCodeGenerationFromStringsCallback callback) {
    Isolate* isolate = Isolate::GetCurrent();
    isolate->SetAllowCodeGenerationFromStringsCallback(callback);
}


bool V8::IsDead() {
    Isolate* isolate = Isolate::GetCurrent();
    return isolate->IsDead();
}


bool V8::AddMessageListener(MessageCallback that, Local<Value> data) {
    Isolate* isolate = Isolate::GetCurrent();
    return isolate->AddMessageListener(that, data);
}


void V8::RemoveMessageListeners(MessageCallback that) {
    Isolate* isolate = Isolate::GetCurrent();
    isolate->RemoveMessageListeners(that);
}


void V8::SetFailedAccessCheckCallbackFunction(
    FailedAccessCheckCallback callback) {
    Isolate* isolate = Isolate::GetCurrent();
    isolate->SetFailedAccessCheckCallbackFunction(callback);
}


void V8::SetCaptureStackTraceForUncaughtExceptions(
    bool capture, int frame_limit, StackTrace::StackTraceOptions options) {
    Isolate* isolate = Isolate::GetCurrent();
    isolate->SetCaptureStackTraceForUncaughtExceptions(capture, frame_limit,
            options);
}


void V8::SetFatalErrorHandler(FatalErrorCallback callback) {
    Isolate* isolate = Isolate::GetCurrent();
    isolate->SetFatalErrorHandler(callback);
}

void V8::RemoveGCPrologueCallback(GCCallback callback) {
    Isolate* isolate = Isolate::GetCurrent();
    isolate->RemoveGCPrologueCallback(
        reinterpret_cast<v8::Isolate::GCCallback>(callback));
}


void V8::RemoveGCEpilogueCallback(GCCallback callback) {
    Isolate* isolate = Isolate::GetCurrent();
    isolate->RemoveGCEpilogueCallback(
        reinterpret_cast<v8::Isolate::GCCallback>(callback));
}

void V8::TerminateExecution(Isolate* isolate) {
    isolate->TerminateExecution();
}


bool V8::IsExecutionTerminating(Isolate* isolate) {
    if (isolate == NULL) {
        isolate = Isolate::GetCurrent();
    }
    return isolate->IsExecutionTerminating();
}


void V8::CancelTerminateExecution(Isolate* isolate) {
    isolate->CancelTerminateExecution();
}


void V8::VisitExternalResources(ExternalResourceVisitor* visitor) {
    Isolate* isolate = Isolate::GetCurrent();
    isolate->VisitExternalResources(visitor);
}


void V8::VisitHandlesWithClassIds(PersistentHandleVisitor* visitor) {
    Isolate* isolate = Isolate::GetCurrent();
    isolate->VisitHandlesWithClassIds(visitor);
}


void V8::VisitHandlesWithClassIds(Isolate* isolate,
                                  PersistentHandleVisitor* visitor) {
    isolate->VisitHandlesWithClassIds(visitor);
}


void V8::VisitHandlesForPartialDependence(Isolate* isolate,
        PersistentHandleVisitor* visitor) {
    isolate->VisitHandlesForPartialDependence(visitor);
}

/**
 * \example shell.cc
 * A simple shell that takes a list of expressions on the
 * command-line and executes them.
 */


/**
 * \example process.cc
 */


}  // namespace v8


#undef TYPE_CHECK


#endif  // INCLUDE_V8_H_
